Index funds take specific indexes as investment targets, such as Shanghai and Shenzhen 300 Index, Standard & Poor's 500 Index, Nasdaq 100 Index, Nikkei 225 Index, etc. Index funds take the constituent stocks of these indexes as the investment targets, and build a portfolio by buying all or part of the weighted constituent stocks of these indexes, and track the performance of these indexes. There are two points in choosing index funds: choose a good index fund to track, and choose an index fund with small investment tracking error, so that investors can obtain relatively good index returns.