What is an index fund?

Simple explanation

An index fund copies a market list (like 'the 500 largest US companies') and just holds those, in the same proportions. No clever stock-picking.

Picture this

A photograph of the whole market. Not a portrait of one face — a snapshot of everyone in the room.

— Cash

Real example

An S&P 500 index fund holds the same 500 US companies, weighted the same way as the S&P 500 index. If the index goes up 8%, your fund goes up roughly 8%.

Common mistake

Thinking 'professional fund managers' beat index funds. Decades of data show the opposite — most managers underperform their index, after fees.

Quick check

Takeaway

Boring + cheap + matching the market = how most long-term investors quietly win.

Related glossary terms