What Is an ETF?
A single tradable share that represents a whole basket of underlying holdings.
An ETF (Exchange-Traded Fund) pools money from many investors to hold a basket of assets — usually stocks or bonds, tracking an index like the S&P 500 — and issues shares against that basket. Buying one ETF share gives you proportional exposure to everything inside it, without buying each underlying holding yourself.
The "exchange-traded" part matters: unlike a traditional mutual fund, which only prices and trades once a day after markets close, an ETF trades continuously on an exchange all day, at a live market price, just like a regular stock.
What actually happens when you buy one ETF share
1
You
Buy 1 share on an exchange
2
The ETF
A pooled basket, priced live all day
3
500+ Holdings
e.g. every S&P 500 company, in index weight
One trade, proportional exposure to everything inside the basket — no need to buy each holding yourself.
Key takeaways
- One ETF share can represent exposure to hundreds or thousands of underlying holdings at once — the main reason they're used for instant diversification.
- An ETF's market price and its true underlying value (NAV) can drift apart briefly intraday, though authorized-participant arbitrage mechanisms usually keep the gap small for liquid funds.
- Not every ETF tracks a broad index passively — some are actively managed, sector-specific, or leveraged. "ETF" describes the wrapper/structure, not the strategy inside it.