In fact, it is easy to understand, and the easiest way to remember is to understand it literally. Formal parameters are formal parameters and real parameters are actual parameters. For example. Fun max(int a, int b) Here A and B can pass any values to them (or change them into others), and here are the formal parameters.

If you want to call this max method, then fun (5,6), where 5,6 are the actual parameters passed in, that is, arguments.