Yes, the fund mainly earns the bid-ask difference, buying at a low level and selling at a high level to obtain income. However, in the process of investment, it is difficult to judge the level. Even if it is sold at a low level, the fund may continue to fall, thus making investors lose money.

Index fund is a kind of fund that tracks a specific index and buys all or part of the constituent stocks in the index in order to obtain the same income as the index.