IB or Introducing Broker program provides you with a commission for each trade performed by your referred clients. The commission is calculated according to your IB Grade based on the trading activity of your clients. The amount of commission paid depends on the order volume, trading pair, and current spread.
You can find more information about the IB commission in this article.
CPA or Cost per Action program provides you with the commission for each introduced trader, who meets the individual criteria and made his first deposit. The requirements for it, as well as the commission amount are calculated individually and the personalised offer is sent to you after joining the CPA program.
Please note that you can join both the IB and the CPA programs.