Index investing, also called indexing, is a method of passive investing whereby a fund (or individual) buys the same stocks in the same proportions as in a target index. The objective of this method is to buy and hold the index.
The return achieved by indexing is the return of the index. If the index tracks a market sector, then the return is that of the sector. If the index tracks the market as a whole, then the return is that of the market. Practitioners of indexing make a conscious decision not to try to outperform the market, rather they decide to obtain the market return.