ETF fund, that is, trading open index fund. As a special type of open-end fund, it combines the advantages of closed-end fund and open-end fund. 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 purchase and redemption must use a basket of stocks for fund shares or a basket of stocks. Because the securities market transaction and the subscription and redemption mechanism exist at the same time, when there is a price difference between the ETF market price and the net value of the fund unit, investors can carry out arbitrage trading. The existence of arbitrage mechanism makes ETF avoid the common discount problem of closed-end funds.

The so-called SSE bond ETF should be an ETF fund that tracks the SSE bond index.