What is an ETF? Definition, how ETFs work and how to buy them

• ETF stands for exchange-traded fund: a fund whose units trade on a stock exchange. In some countries it is also called a tracker or a listed index fund.
• It follows an index, up and down. An ETF guarantees nothing: if the index loses 30%, the ETF loses about as much.
• Its fees are low. In the US, index equity ETFs cost 0.14% a year on average in 2025, against 0.40% for equity mutual funds, according to the ICI.
• You buy it through a broker, in a taxable brokerage account or a tax-advantaged one (an IRA in the US, an ISA in the UK, a PEA in France), by placing a stock order.

ETFs have reshaped investing in thirty years. The first US ETF, State Street's SPDR S&P 500, launched on January 22, 1993. At the end of August 2026, ETFs worldwide managed a record $24.03 trillion across 17,713 funds listed on 86 exchanges, according to the research firm ETFGI. Three providers, iShares, Vanguard and State Street, held almost 59% of it.

This guide explains what an ETF is and how it works, the main types, what it really costs, its risks, how it differs from a stock or a mutual fund, then how to buy one step by step, and which account to hold it in depending on your country. The figures quoted are dated and sourced.

What does ETF stand for?

ETF stands for exchange-traded fund. It is a pooled investment fund whose units are listed and traded continuously on a stock exchange, like shares. In France it is often called a tracker, because it tracks an index, and the terms ETF, exchange-traded fund and listed index fund all describe the same thing.

The idea fits in one sentence: instead of buying the 500 companies of the S&P 500 one by one, you buy a unit of a fund that holds all of them, in the same proportions as the index. When the index rises 1%, the unit rises by about 1%, minus fees; when it falls, the unit falls just as much.

How an ETF works

An ETF is run by an asset manager, which buys the securities in the index or obtains their performance, and keeps them with a custodian separate from the manager, as fund regulation requires. The ETF's units then trade on the exchange throughout the session, at a price that follows the value of the securities held.

Two markets coexist, explains FINRA, the US broker regulator. In the primary market, large firms called authorized participants create or redeem units directly with the ETF, in blocks worth millions of dollars. In the secondary market, where individuals trade, investors buy and sell units among themselves. This mechanism keeps the ETF's price close to the value of its portfolio without pinning it there: it can drift away, especially in thinly traded markets.

Physical or synthetic replication

A physically replicated ETF actually holds the securities in the index, in full or in part: it is the most common model, according to France's market regulator, the AMF. A synthetic ETF does not hold the index securities: it signs a performance swap with a bank, which pays it the index return. The technique can, for instance, bring global shares into a French PEA, but it adds a risk on the bank that signs the contract.

Accumulating or distributing

A distributing ETF pays out the companies' dividends to unit holders, usually one to four times a year. An accumulating ETF reinvests them automatically inside the fund. The first suits someone looking for income, the second someone who wants their capital to grow without thinking about it, and depending on the country and the account, it avoids being taxed on dividends you never meant to spend.

Types of ETFs

• Equity ETFs, on a broad index (S&P 500, MSCI World, Euro Stoxx 50), a region (emerging markets), a sector (healthcare, technology) or a theme. They are the most widely used for long-term investing.
• Bond ETFs, which hold government or corporate bonds. They are often used to cushion the swings of a stock portfolio.
• Commodity products, such as gold. Some hold the metal in a vault, others use futures contracts: their documents say which. In Europe, many take the form of ETCs, debt securities rather than funds, and in the US many are structured as trusts or commodity pools.
• Leveraged and inverse ETFs, which amplify or reverse the index's move over a single day. FINRA warns they are not designed to be held beyond that short period, and the AMF calls them highly speculative.
• Active ETFs, where a manager picks the securities and tries to beat the index. Their holdings and performance drift from the index, and their fees are often higher.

How much does an ETF cost?

The first cost is the annual management fee, called the expense ratio or TER, taken directly from the fund's value: you never see it charged, but it reduces performance every day. The AMF puts most ETFs below 0.5% a year, against more than 1% for an actively managed fund. In the US, the Investment Company Institute measured an asset-weighted average of 0.14% in 2025 for index equity ETFs, against 0.40% for equity mutual funds.

On top of that come the broker's charges: a commission on each purchase and sale where the broker still charges one, sometimes custody fees, and the gap between the buying and selling prices shown on the exchange (the bid-ask spread), tight on large ETFs and wider on thinly traded ones. The true cost finally shows in the tracking difference: the gap, over a year, between the ETF's performance and its index's.

These gaps look tiny, but they are not over time. As an illustration, 10,000 invested for thirty years in a market returning 6% a year grows to 54,271 with 0.2% in annual fees, and to 37,453 with 1.5%: a difference of 16,818, for the same stake and the same market. The compound interest calculator reruns the numbers with your own amounts, fees included.

ETF vs stock vs mutual fund

Compared with a stock, an ETF trades the chance of landing the next big winner for the certainty of owning the whole market, winners and losers alike. Compared with a mutual fund, it brings lower fees and continuous trading; an unlisted index fund, on the other hand, may enjoy tax advantages of its own depending on the country. The guide to what stocks are covers the basics.

The risks of an ETF

• Capital loss. An ETF follows its index both ways. A global equity ETF can lose a third of its value in a few months during a crisis.
• Tracking difference. Performance can drift from the index's, because of fees, the replication method or dividend taxation.
• Liquidity. On thinly traded securities (small companies, emerging markets, some bonds), trading costs rise and the price can move away from the index value.
• Currency. An ETF of US stocks bought in euros or pounds also moves with the dollar.
• Counterparty risk, for a synthetic ETF, which depends on the bank it signed its swap with.
• Hidden concentration. Two ETFs can overlap, the AMF warns: a world ETF and a technology ETF partly hold the same US giants.

Are ETFs safe?

They are safe in their structure, not in their returns. The fund's assets are kept separate from the manager's and held by a custodian: if the manager went bankrupt, the fund's securities would still belong to the unit holders. But nothing protects you from the market itself falling. An equity ETF suits money that can stay invested for eight years or more, not an emergency fund.

How to buy ETFs, step by step

1. Open an account with a broker or your bank: a taxable brokerage account, or a tax-advantaged account if your country offers one (see below). The firm must be licensed to provide investment services.
2. Choose the index before the ETF. A global index (MSCI World, MSCI ACWI) spreads risk across thousands of companies; a single-country or sector index concentrates it.
3. Compare the ETFs that track that index: annual fees, fund size (a fund that is too small may close), replication method, currency, accumulating or distributing.
4. Read the key information document (KID) or the fact sheet and prospectus, which give the risk level, the fees and the performance scenarios.
5. Place a limit order during exchange hours rather than a market order, so you do not pay more than planned if the spread widens.
6. Invest regularly rather than all at once: a fixed amount every month spares you from guessing the right moment and smooths your purchase price.

Where to hold ETFs, by country

The ETF is the same everywhere; the tax on its gains depends on the account that holds it. The rules below are general pointers, to check against your country's official sources.

• United States: a brokerage account, where many brokers no longer charge commissions on ETFs, or a tax-advantaged retirement account (IRA, 401(k)). FINRA notes that ETFs often distribute fewer capital gains than comparable funds, hence their reputation for tax efficiency.
• United Kingdom: the Stocks and Shares ISA, into which you can pay up to £20,000 per tax year, with gains and dividends tax-free.
• France: the PEA accepts eligible ETFs, those invested at least 75% in European Union shares, many world ETFs qualifying through synthetic replication; life insurance policies offer them as unit-linked funds; an ordinary securities account accepts everything, with a 31.4% tax on gains in 2026.
• Spain: ETFs do not benefit from the traspasos regime of investment funds, which lets you switch from one fund to another without tax; every ETF sale is taxed in the savings income base, the CNMV notes.
• Brazil: ETFs are listed on the B3, but equity ETFs do not get the R$20,000 monthly sales exemption that shares enjoy, according to the B3; the rate and payment of the tax should be checked with the Receita Federal.

For readers in France, the guide to where to put your money in France in 2026 covers the choice between the PEA, life insurance and an ordinary account, and where ETFs fit in your overall savings.

How much to invest, and for how long?

An equity ETF is judged over years, not weeks. Before putting anything into one, build an emergency fund of three to six months of spending in accessible, guaranteed accounts. After that, the share in equity ETFs depends on how big a drop you can sit through without selling: if a 30% fall would make you sell everything, that share should stay small.

Time does the rest. With 200 a month for thirty years in a market returning 6% a year, the gap between 0.2% and 1.5% in fees comes to almost 39,000 at the end, 188,012 against 149,413. Past performance does not predict future returns, and these figures only illustrate the weight of fees and time.

Tradoshi's portfolio tracking keeps your cost basis line by line, ETFs included, and compares the allocation you aim for with the one you actually have, so you know when to rebalance.

This guide is educational and is not personalized investment advice. Any investment in ETFs carries a risk of capital loss; the figures quoted are dated and will be updated.

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