ETF is the abbreviation of English (Exchange-traded Fund), which is usually translated as "Exchange-traded Fund", and the Shanghai Stock Exchange calls it "Transactional Open Index Fund". ETF is a fund operation mode with variable fund share, which combines the operation characteristics of open-end fund and closed-end fund. On the one hand, it can be bought and sold in the secondary market of the exchange like a closed-end fund, and on the other hand, it can be purchased and redeemed like an open-end fund, but its purchase is to exchange a package of shares for ETF shares, and it is also to exchange a package of shares instead of cash when redeeming.