How ETFs Work and Why Investors Use Them

What an ETF is and how it differs from a mutual fund

An ETF (exchange-traded fund) is a basket of investments — usually stocks, bonds, or a mix of both — that you buy and sell on a stock exchange the same way you would buy a single company's stock. You place an order through a brokerage, the trade happens during market hours, and you own a share of everything inside that basket.

The key difference from a mutual fund is how you trade it. A mutual fund's price is set once per day after the market closes, and you buy or sell directly from the fund company. An ETF's price changes throughout the trading day as buyers and sellers trade it back and forth, just like Apple or Microsoft stock. This means you can sell an ETF immediately if you need the money, whereas a mutual fund order placed at 2 p.m. won't execute until after 4 p.m. when the market closes.

ETFs also tend to have lower fees than actively managed mutual funds because most ETFs simply track an index — a fixed list of companies or bonds — rather than paying a manager to pick investments. You'll pay a small annual expense ratio (the yearly cost as a percentage of what you own) plus a trading commission when you buy or sell, though many brokerages now charge zero commission on ETF trades.

Key Takeaways

• An ETF is a collection of investments you buy as a single unit on a stock exchange, with a price that changes throughout the trading day.
• Most ETFs track an index, meaning they hold the same stocks or bonds in the same proportions as a published list, which keeps costs low.
• You can sell an ETF instantly during market hours if you need the money, unlike a mutual fund which processes sales once per day.
• ETFs typically charge lower annual fees than actively managed mutual funds because they don't require a manager to pick individual investments.
• You can hold an ETF in a regular taxable brokerage account or inside a retirement account like a 401(k) or IRA.

How an ETF holds and tracks investments

Inside an ETF is a portfolio of individual securities — the actual stocks or bonds the fund owns. If you buy an S&P 500 ETF, you own a tiny slice of all 500 companies in that index. The fund company buys those 500 stocks and holds them, and you own shares of the fund itself, not the stocks directly.

The fund's price moves with the value of what's inside it. If the 500 companies in an S&P 500 ETF gain 2% in value, the ETF's share price rises roughly 2% (minus the small annual fee). This is called tracking — the ETF follows the index it's designed to mirror.

Some ETFs track broad indexes like the S&P 500 or the total U.S. stock market. Others track narrower slices: technology stocks only, emerging-market bonds, dividend-paying companies, or real estate investment trusts. A few ETFs use active management, meaning a manager picks the holdings rather than following an index, but these are less common and charge higher fees.

Why investors choose ETFs over individual stocks

Buying individual stocks means betting on specific companies. If you pick wrong, that stock can fall sharply and take a large chunk of your money with it. An ETF spreads your money across dozens or hundreds of companies, so no single bad pick can sink your portfolio. This is called diversification.

Diversification also means you don't have to research individual companies. You don't need to read earnings reports or understand whether a company's new product will succeed. You simply own a slice of an entire market segment or the whole market, and you benefit from the average return of all those companies combined.

ETFs also make it easier to build a simple portfolio. Many investors hold just three or four ETFs — one for U.S. stocks, one for international stocks, one for bonds, and perhaps one for real estate — and rebalance once or twice a year. This approach requires far less time and attention than picking individual stocks, and research shows it often outperforms investors who trade frequently.

The costs of owning an ETF

When you buy an ETF, you pay two types of costs. The first is the expense ratio, an annual fee charged by the fund company for holding and managing the portfolio. For a broad stock index ETF, this is typically 0.03% to 0.10% per year — meaning if you own $10,000 in the ETF, you pay $3 to $10 per year. For more specialized ETFs (emerging markets, bonds, real estate), the ratio might be 0.20% to 0.50% or higher.

The second cost is the trading commission, which you pay when you buy or sell. Most major brokerages (Fidelity, Schwab, Vanguard, E*TRADE, Interactive Brokers) charge zero commission on ETF trades, so this cost has largely disappeared for retail investors. Some smaller or older brokerages may still charge $5 to $10 per trade, so check your broker's fee schedule before you open an account.

You may also encounter a bid-ask spread — the difference between the price someone will pay for the ETF and the price someone will sell it for. For popular, heavily traded ETFs, this spread is tiny (a penny or two per share). For obscure or thinly traded ETFs, the spread can be wider, which means you lose a bit more money on the trade itself. Stick to ETFs with high trading volume to keep this cost minimal.

ETFs in retirement and taxable accounts

You can hold an ETF in almost any type of investment account. In a 401(k) or 403(b) (employer retirement plans), your employer usually offers a menu of ETFs and mutual funds to choose from. In an IRA (individual retirement account), you can buy almost any ETF through a brokerage. In a regular taxable brokerage account, you have access to all publicly traded ETFs.

ETFs are tax-efficient compared to actively managed mutual funds because they rarely distribute capital gains to shareholders. When a mutual fund manager sells a stock at a profit, that gain is passed to all fund owners and triggers a tax bill. ETFs avoid this through a mechanism called in-kind redemption, which allows large investors to exchange their shares for the underlying stocks without triggering a taxable event. This is one reason ETFs work well in taxable accounts where you want to minimize taxes.

In a retirement account, the tax advantage matters less because the account itself is tax-deferred or tax-free. You can hold either ETFs or mutual funds and pay no tax on gains until you withdraw the money (or never, in a Roth account). Many investors choose ETFs in retirement accounts simply because the fees are lower.

Common types of ETFs and what they track

The most popular ETFs track broad stock indexes. The SPY, IVV, and VOO all track the S&P 500 (500 large U.S. companies). The VTI and ITOT track the entire U.S. stock market, including mid-size and small companies. The VXUS and IXUS track international stocks outside the U.S. These core holdings form the backbone of most simple portfolios.

Bond ETFs track fixed-income indexes. The BND and AGG track the broad U.S. bond market (government, corporate, and mortgage bonds). The VCIT and LQD track corporate bonds. The VGIT and SHV track shorter-term bonds, which are less sensitive to interest-rate changes. The VWOB and EMBD track emerging-market bonds, which offer higher yields but more risk.

Specialized ETFs track narrower segments: technology stocks (QQQ, VGT), dividend-paying stocks (VYM, SCHD), real estate (VNQ, XLRE), commodities (GLD for gold, USO for oil), and many others. These can be useful for tilting a portfolio toward a specific area, but they're not necessary for a basic diversified portfolio. Most investors do better starting with broad index ETFs and adding specialized ones only if they have a specific reason.

How to choose an ETF for your portfolio

Start by deciding what you want to own: U.S. stocks, international stocks, bonds, or a mix. Then look for the lowest-cost ETF that tracks that category. For U.S. stocks, compare the expense ratios of VOO (Vanguard), IVV (BlackRock), and VTI (Vanguard). For bonds, compare BND (Vanguard) and AGG (BlackRock). The difference in cost is small, but over decades it compounds.

Check the trading volume to make sure the ETF is liquid. Look at the average daily volume in shares — anything above 100,000 shares per day is fine for most investors. Very new or very specialized ETFs might have lower volume, which widens the bid-ask spread and makes trading more expensive.

Avoid chasing performance. An ETF that was the best performer last year is not may provide to be the best this year. Stick to broad, low-cost index ETFs and rebalance once or twice per year. This simple approach has beaten most active investors over the long term.

Frequently Asked Questions

Can I lose all my money in an ETF?

If the ETF tracks an index like the S&P 500, you can lose money if the stock market falls, but you won't lose everything unless the entire U.S. economy collapses. Diversified ETFs spread risk across many companies. Specialized ETFs (single-sector, single-country, or commodity ETFs) can fall much further if that sector or country struggles, but even then, a complete loss is rare.

Do I get dividends from an ETF?

Yes. If the stocks or bonds inside the ETF pay dividends or interest, the ETF collects that money and distributes it to shareholders, usually once or four times per year. You can take the dividend as cash or reinvest it to buy more shares. Most brokerages offer automatic dividend reinvestment at no cost.

What's the difference between an ETF and an index fund?

An index fund is a mutual fund that tracks an index. An ETF also tracks an index but trades on an exchange like a stock. Both are low-cost and diversified, but ETFs trade throughout the day and are more tax-efficient, while index mutual funds trade once per day. For most investors, ETFs are the better choice today.

Can I buy an ETF with a small amount of money?

Yes. You can buy a single share of almost any ETF, and many ETFs trade for $50 to $200 per share. Some brokerages also offer fractional shares, meaning you can invest any dollar amount, even $1, and own a piece of an ETF. This makes ETFs accessible to investors with small accounts.

Should I buy an ETF or a mutual fund?

For most investors, an ETF is the better choice today. ETFs have lower fees, trade during market hours, and are more tax-efficient. Mutual funds still make sense if your employer 401(k) offers only mutual funds, or if you want automatic dividend reinvestment and don't mind waiting until after market close to sell.