Bogleheads:Featured article/Index fund

An index fund is a fund that pools investors capital for the purpose of investing in securities, typically a mutual fund or exchange-traded fund (ETF), that aims to replicate the movements of an index of a specific financial market.

A well-managed index fund provides investors with a simple way to access such advantages as low costs, improved tax efficiency, style consistency and reduced manager risk. Investors should be mindful that not all index funds are low cost and that some indexes can be exploited by active investors when the indexes periodically reconstitute.

The key measure for accessing an index fund's efficiency is how well it tracks its benchmark index. (more...)