The so-called IB agent is the intermediary. If you open an account through IB, the dealer will pay IB a commission every time you trade, and this commission is of course from the sheep or from you, so now some IB are willing to return part of the commission they get to their customers, which is called IB rebate, so it is also good to choose a reputable IB who is willing to rebate, which can reduce their transaction costs.