ETF is the abbreviation of Exchange Traded Fund in English, literally translated as "exchange traded fund" (in fact, this name was often used in China before), but in order to highlight the connotation and essential characteristics of this financial product, ETF is now generally called "transactional open index fund". ETF is an open-end fund that tracks the changes of the "underlying index" and is listed on the exchange. Investors can buy and sell indexes by buying and selling ETFs just like buying and selling stocks. Therefore, ETF can be understood as "a stock index investment product". Investors can buy or redeem fund shares from fund management companies, and at the same time they can buy and sell ETF shares at market prices in the securities market like closed-end funds. However, the subscription and redemption of ETF must be exchanged for fund shares with a basket of stocks, or exchanged for fund shares with a basket of stocks, which is one of the main characteristics that ETF is different from other open-end funds. Compared with traditional closed-end funds and open-end funds, ETF has many advantages.