Glossary · Markets · Beginner-friendly
Index
In plain English
An index is a scoreboard for a market or group of stocks (like the S&P 500). You don’t buy the index itself - you usually buy a fund that follows it.
Everyday analogy: Like a league table that tracks the whole season, not one player.
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Why it matters
Indices set the scoreboard for markets and the benchmarks behind countless ETFs and performance claims.
A bit more detail (optional)
What an index is (and isn’t)
An index is a measurement tool, not a fund you buy directly. Products like ETFs and futures are how investors get index exposure.
Weighting schemes
Market-cap weighted indices give bigger companies more influence. Equal-weight and other schemes change leadership and volatility.
Simple examples
Beating the index
Active managers often compare returns to a stated benchmark. Fees and risk differences matter as much as the headline beat or miss.
Cap-weight concentration
When a handful of mega-caps lead, the index can rise while most members lag - breadth tells a different story than the headline level.
Easy mistakes to avoid
- Thinking you can “buy the index” without a fund or derivative
- Comparing a strategy to the wrong benchmark
- Ignoring weighting (mega-caps can dominate cap-weighted indices)
Remember: Know which index you’re measuring against - and how it’s built.