Quick answer
An exchange-traded fund (ETF) is an SEC-registered fund that pools money into stocks, bonds or other assets, but its shares trade on a stock exchange throughout the day at market prices. You buy from and sell to other investors through a broker, not from the fund itself [1].
Key points
- An ETF is a pooled fund whose shares are listed on a stock exchange.
- You trade ETF shares with other investors during the day, at a market price that can differ slightly from NAV.
- Only large firms called Authorized Participants create and redeem shares directly with the fund, in big blocks.
- Trading costs include the bid-ask spread and any broker commission, on top of the fund's yearly expenses.
- Leveraged and inverse ETFs reset daily and are generally not suitable for buy-and-hold investors.
#What is an ETF in plain terms?
An ETF is a fund — a pool of money that buys many investments at once — whose shares are listed on a stock exchange. The SEC explains that, like mutual funds, ETFs are SEC-registered investment companies that let investors pool money in stocks, bonds, other assets or a mix [1]. The difference is how you get in and out.
With a mutual fund, you buy from the fund at the end-of-day price. With an ETF, you buy from another investor on the exchange, at whatever the market price is when your order fills. ETF shares "are traded throughout the day on national stock exchanges," according to the SEC's ETF bulletin [2]. Each ETF has a ticker symbol, just like a company's stock.
#How are ETF shares created and redeemed?
ETF shares come into existence through a two-level system. At the top, a small group of large financial firms called Authorized Participants (APs) deal directly with the fund. The SEC says typically only APs buy and redeem shares directly from the ETF, and only in large blocks (for example, 50,000 shares) called creation units [2].
To create shares, an AP assembles and deposits a designated basket of securities and cash with the ETF, and receives ETF shares in return [2]. To redeem, the process runs the other way: the AP hands back a creation unit and receives securities or cash. The AP can then sell the new shares on the exchange, where everyone else trades.
Creation, then trading
Why does this matter to a beginner? Because it explains why an ETF's market price usually stays close to the value of what it holds. Because APs can trade directly with the ETF at NAV as well as on the market, they can profit when the two drift apart; the SEC says the expected result of this arbitrage is that the market price moves back in line with NAV per share [2]. Nothing guarantees a perfect match, though.
#Why can an ETF's price differ from its NAV?
Like a mutual fund, an ETF calculates a net asset value — assets minus liabilities, per share. But you do not trade at NAV. The SEC notes that an ETF's market price "typically will be more or less than the fund's NAV per share" — called trading at a premium or a discount [2]. For large, heavily traded ETFs this gap is often small; for thinly traded ones it can be wider.
| Term | What it means | Why it matters |
|---|---|---|
| NAV per share | Value of the fund's holdings minus liabilities, divided by shares | The benchmark for what each share is worth |
| Market price | The price at which shares actually trade on the exchange | What you pay or receive |
| Premium / discount | Market price above / below NAV | You may pay a little more, or sell for a little less, than the holdings are worth |
| Bid / ask | Highest price buyers offer / lowest price sellers accept | The gap between them is a trading cost |
#What does it cost to trade an ETF?
ETFs generally do not charge fees directly to investors for buying or selling shares, but you may pay other costs such as a broker's commission [3]. There is also the bid-ask spread: the bid is lower than the ask, and the SEC points out that spreads reduce potential returns [2]. See our glossary entry on the bid-ask spread. On top of trading costs, every ETF charges a yearly expense ratio taken from fund assets.
Worked example
The cost of a round trip
A hypothetical ETF shows a bid of $50.00 and an ask of $50.04. Its NAV per share is $50.01. You buy 100 shares, then change your mind and sell right away. Assume no commission.
- Buy 100 shares at the ask (100 × $50.04)
- $5,004.00
- Sell 100 shares at the bid (100 × $50.00)
- $5,000.00
- Spread cost of the round trip
- $4.00 (about 0.08% of $5,004)
- Ask vs NAV (($50.04 − $50.01) ÷ $50.01)
- about 0.06% premium
Even with zero commission, buying and selling immediately cost $4. Trading the same ETF often repeats that cost each time.
Hypothetical prices for illustration; percentages calculated in Python and rounded.
#Are all ETFs index funds?
No. The SEC says ETFs "can be index-based or actively managed" [2]. An index-based ETF tries to track a market index such as a broad stock index; see index funds explained. An actively managed ETF has a manager choosing holdings.
Some ETFs are built for short-term trading. Leveraged ETFs seek a multiple of an index's daily return, and inverse ETFs seek the opposite of it. The SEC warns that their performance over periods longer than one day "can differ significantly from their stated daily performance objectives" and that they are generally not suitable for buy-and-hold investors [4].
Common beginner mistakes
Treating ETF trades as free
Zero commission is not zero cost. The bid-ask spread and any premium or discount to NAV still affect what you pay and receive.
Using market orders in thin trading
When few shares trade, spreads can be wide. A limit order lets you set the most you will pay; see market vs limit orders.
Holding a leveraged ETF long term
Daily-reset funds are designed for one-day goals. Over weeks or months, their returns can drift far from a simple multiple of the index.
Assuming "ETF" means "safe"
An ETF is a wrapper. Its risk comes from what it holds — a single-sector or bond ETF behaves very differently from a broad stock ETF.
What's the bottom line?
An ETF combines a fund's diversified basket with a stock's trading mechanics. Large firms create and redeem shares behind the scenes, while you trade on an exchange at a market price that sits close to — but not exactly at — NAV. Keep an eye on the spread, the expense ratio and the fund's objective, then see how it stacks up in ETF vs mutual fund.
Frequently asked questions
Can I buy an ETF directly from the fund company?
Generally no. Retail investors buy and sell ETF shares on an exchange through a broker. Only Authorized Participants deal directly with the fund, in large creation units.
Do ETFs pay dividends?
Many ETFs that hold dividend-paying stocks or interest-paying bonds pass that income to shareholders as distributions. The fund's prospectus explains how and when.
Is an ETF a mutual fund?
No, though both are SEC-registered investment companies. The key difference is that ETF shares trade on an exchange at market prices during the day, while mutual fund shares are bought from and sold to the fund at end-of-day NAV.
What is a creation unit?
A large block of ETF shares — the SEC gives 50,000 shares as an example — that an Authorized Participant creates or redeems directly with the fund in exchange for a basket of securities and cash.
Sources
Grade A = primary source (regulator, government agency, official rulebook or the index provider's own documents). Numbers in brackets in the text point here.
- U.S. Securities and Exchange Commission. Mutual Funds and ETFs: A Guide for Investors (2016). Accessed 2026-10-03.A
- U.S. SEC — Investor.gov. Updated Investor Bulletin: Exchange-Traded Funds (ETFs) (2023). Accessed 2026-10-03.A
- U.S. SEC — Investor.gov. Characteristics of Mutual Funds and Exchange-Traded Funds (ETFs) – Investor Bulletin (2025). Accessed 2026-10-03.A
- U.S. SEC — Investor.gov. Updated Investor Bulletin: Leveraged and Inverse ETFs (2023). Accessed 2026-10-03.A
This page is general education, not personal financial, tax or legal advice. Figures in worked examples are hypothetical and calculated before taxes and fees unless stated. Rules and limits change; check the linked primary sources for the current version. How we check every page.
