For the investment market with exchanges, there are mainly two trading mechanisms: market maker system and market maker system.

Matchmaking system means that the exchange department participates in the transaction and only makes analogy analysis on investment orders. For example, the stock market is a comprehensive comparison between buying and selling. If a price can promote the maximum transaction volume, then this price is determined as the transaction price, and then the order is paid from high to low, and the order is sold from low to high.

The biggest feature of the matchmaking system is that the exchange itself does not participate in the transaction, and investors buy and sell each other. Therefore, there are usually orders hanging too low and orders hanging too high that cannot be closed. If the price is the same, which order has been sold first in chronological order?