Index funds are typically structured as either mutual funds or exchange-traded funds, but investors can manually recreate an index through 'direct indexing.'

ETFs and mutual funds both pool money into a basket of investments—but the key difference between them is that mutual funds trade just once per day after the market closes, while ETFs trade like stocks throughout the day at fluctuating prices.

A stock index is a group of companies clustered together, often providing a condensed snapshot of a market segment.

Investing in mutual funds can give you access to a wide range of securities, such as stocks and bonds, with just a single investment.

Vanguard Group founder Jack Bogle created the first index fund, the Vanguard 500, in 1976—but the fund didn't take off until the 1990s.

Explore a list of the world's largest mutual funds.

Mutual funds are categorized as stock, bond, money market, and target-date funds.

ETFs were first created as an alternative to mutual funds, combining the diversification benefits of a mutual fund with the ability to trade throughout the day on a stock exchange.

Explore a step-by-step guide for getting started as a retail investor

Instead of purchasing individual stocks and bonds, new investors may want to start in funds that track an index—like the S&P 500—or that hold a group of themed stocks.

How mutual funds work

Mutual funds function similarly to other types of investments. If you want to invest, you go through a brokerage firm. However, they have a few key differentiators. Most are actively managed by a broker instead of passively earning you returns. Plus, they can carry some hefty fees.

Mutual funds invest in multiple different companies with money from many investors, while an individual stock represents ownership in a single company and is bought by individual investors.

The S&P 500, managed by the same company, is another major stock index

Also run by S&P Dow Jones Indices, the S&P 500 tracks 500 large US firms using market-value weighting. Many analysts view it as a more accurate gauge of the American economy.

Investors rely on the S&P 500 as a benchmark for the state of the economy

Since the index represents a broad range of diverse industries, it's become a proxy for the market itself and a common benchmark for investors to compare returns and performance patterns against. Generally speaking, when someone says a stock is under- or out-performing the market, that actually means under- or out-performing the S&P 500. The S&P 500 is exchange-agnostic, and includes companies listed on both the NYSE and Nasdaq.

Mutual funds pool money to create larger investment opportunities with higher returns for anyone who initially invests in the fund.

Contrary to popular belief, random investments can outperform managed funds.

Some argue that the S&P 500 is actually an actively managed index

Some critics of the S&P 500's selection process argue that human involvement makes it an actively managed index. S&P Global maintains that while a human selects the stocks in the index, those decisions are not made with the intent of maximizing performance, but rather, to provide a snapshot of the largest companies across different industries.

A bond ETF lets someone invest in multiple bonds through one single fund

There are risks, there are also major perks to buying a bond ETF, like the ability to purchase bonds on the stock market.

The 'Big Three' asset managers—Vanguard, State Street, and BlackRock—collectively manage more than $30T in assets and are the largest shareholders in roughly 88% of all the companies listed on the S&P 500.

BlackRock says investor demand and improvements in underlying fund technology have supercharged ETF availability in 2025

Investors are likely most familiar with ETFs that invest in an index or other grouping of stocks. However, BlackRock breaks down a wide variety of options, including commodity ETFs, currency ETFs, and bond ETFs.

The Dow Jones Industrial Average vs. the S&P 500: Which one is a better representation of the economy?

The Dow and S&P 500 are both indexes meant to provide a broad representation of the economy. The Dow has 30 companies and is weighted by share price, while the S&P 500 has 500 different companies weighted by market capitalization. Since the indexes are so different, investors don't always agree on which index is a better representation of the economy—though the two move in the same direction more than 90% of the time.

Learn how to invest in index funds with this step-by-step guide.

There are more than 300 different thematic ETFs

Exchange-traded funds seem to offer something for everyone. As tracked by ETF.com, there are 338 thematic ETFs, offering exposure to “baskets” of stocks covering global infrastructure, genomics, cannabis, and more.

Open-end and closed-end mutual funds differ in how they create and distribute shares.

Mutual funds come with a few associated fees.

Active investors try to 'beat' the stock market's performance

There are two primary types of investment strategies that professional investors use: active investing and passive investing. While active investors try to "beat" the stock market's performance, passive investors have a bit more faith in the system.

Mutual fund share classes are rankings of different types of services for investors.

In the early 2000s, Warren Buffett invested $1M in an index fund to show that passively managed investments would outperform hedge funds—making the point that actively managed funds are not worth the management fees they charge.

ETFs and mutual funds are both taxed on capital gains and on dividends.

Test your ETF knowledge

A 10-question quiz from the SEC allows investors to test their basic knowledge about exchange-traded funds and their investing counterparts, mutual funds. Here’s a sample question: Is the past performance of a fund a good indicator of future results? (Hint, the answer is no).

Read about the pros and cons of mutual funds.

The pros of exchange-traded funds include ease of access through brokerage apps and retirement savings accounts

One unexpected perk is that ETFs are typically associated with lower capital gains tax requirements. Read this list to learn more about the benefits of investing in ETFs.

Explore a giant ETF database

Given that there are more than 3,000 ETFs trading in the US, the list of options for individual investors may be overwhelming. VettaFi provides a database that allows potential investors to sort funds by sector, region, strategy, fund issuers, and more. It tracks nearly 100 funds focused on general technology but just one that focuses on copper mining.

The SPDR S&P 500 ETF is one of the most highly traded funds on the market

State Street, a popular ETF issuer, is responsible for the SPDR S&P 500 ETF. This fund trades under the SPY ticker, and State Street maintains a web page with key facts and figures on SPY. For instance, its expense ratio is 0.0945%, or $9.45 on an initial $10K investment.

The Dow Jones Industrial Average is a stock market index

The Dow Jones Industrial Average tracks 30 large U.S. companies from all major U.S. sectors except for utilities and transportation. It's considered a bellwether of the U.S. economy.

Read how Vanguard's founder used the S&P 500 to revolutionize retail investing

John Bogle, the founder of The Vanguard Group, created a fund that tracked the S&P 500 in 1976. That fund created an unprecedented opportunity for individual retail investors, brought down fees across the board, and popularized the belief that passive, low-cost index fund investments would outperform actively managed portfolios long-term.

There are monthly dividend ETFs that pay you to hold them

Traditional dividend stocks and funds pay out quarterly, or four times a year. A select group of stocks and funds pay out monthly, putting cash in investors’ hands 12 times a year. These monthly dividend funds are popular because their regular payouts can help keep budgets on track.

See the top 100 ETFs by trading volume

This list grabs the top 100 by trading volume, or the average number of shares that have traded hands over a 3-month period. Top of the list is a semiconductor-focused fund from Direxion, followed by other tech-centric offerings.

Leveraged ETFs made headlines in 2026 as a boom in single-stock leveraged products tied to AI companies drove volatility and record retail demand.

ETFs are rising in popularity

While less than half of retail investors hold ETFs in their portfolio, this figure is up dramatically in recent years, and experts forecast continued adoption as more options hit the market and total ETF assets under management continue to grow.

Millions of Americans will be invested in SpaceX because of the fast-tracked process to list SpaceX on the Nasdaq 100, and, subsequently, the index funds that track it.

Dow components are chosen by a committee, not a formula

Unlike many indices, the Dow has no strict rules for inclusion. A small committee at S&P Dow Jones Indices uses judgment—favoring companies with strong reputations, steady growth, and broad investor interest.

Mutual fund investors typically must pay a variety of different types of taxes associated with their investment, unless the funds are within tax-advantaged accounts like a 401(k) or IRA.

Why some say the S&P 500 has effectively become an AI fund

The S&P 500 is a market-cap-weighted index, which means companies with larger market capitalizations have a larger impact on the index's overall performance. Many of the top companies in the index are currently tech companies—including Nvidia, Microsoft, Alphabet, and Apple—that all have large investments in artificial intelligence. As a result, some analysts are concerned that the index is overly exposed to risky AI investments.

Retail investors cannot directly invest in private credit funds—but other financial vehicles can offer exposure to the industry

For example, as some US regulations have loosened in recent years, retail investors have begun to get exposure to the private credit market via ETFs that invest in publicly traded financial vehicles with private credit exposure, such as BDCs.

Before the S&P 500 launched in 1957, Standard and Poor's had a daily index with just 90 companies

Unlike previous indexes from S&P, the S&P 500 could be computed in real time using computer technology that tracked stock tickers across stock exchanges. This innovation is partly what led to 500 companies being listed on the index, a huge increase from the 90 companies in S&P's flagship index when the company had to do all the analysis by hand.

Biotech ETFs allow investors to gain exposure to multiple promising companies in the industry

Biotech ETFs offer a diversified alternative to purchasing an individual biotech stock and gambling on whether an individual company’s clinical trial yields the next blockbuster cancer treatment or an absolute flop. This list of the top biotech ETFs in 2025 can help you learn more about them.

Watch how the S&P 500 is actually calculated

After accounting for each company's float-adjusted market capitalization (a metric that combines the price of a company's stock, the total number of shares, and the stock's float, which means how many shares are actually available), the S&P 500 formula uses a divisor to create the index number. However, what the divisor is and what it represents are secrets.

A direct listing is when a company goes public, listing shares on a stock exchange

A direct listing is when a company goes public, listing its shares on a stock exchange, rather than issuing new shares or raising capital. That means investment banks—traditionally serving as intermediaries—could lose out on some of the profits from these deals as more companies like Spotify opt for direct listings.

Hedge funds make money from imposing steep fees on investors, as well as from investment performance

Hedge funds often operate on a "2 and 20" model: Investors pay fund managers a 2% management fee, and the hedge fund keeps 20% of their profits. (The 2% is imposed annually, irrespective of performance.) Hedge funds are known for chasing big returns—and taking big risks to get them. This explainer not only breaks down how they work in detail, but also the strategy first introduced in 1949 that still shapes hedge fund investing today.

Some institutional investors are growing wary of private equity, as certain investments underperform traditional market indices

Private equity often attracts investors who can afford to tie up capital for long periods of time in exchange for higher returns than traditional investments. For many years, private equity at least tracked with the S&P 500 in terms of returns to investors, but in 2024 and 2025, it underperformed and posted declining returns.

Retail investors are individuals who trade stock for themselves

Institutional investors, on the other hand, are investing for someone else. There are big differences between the two, one being that institutional investors can be granted certain special treatment (like being able to purchase IPOs right away).