what happens by using stringify in the following example?

Here is the code where I am using STRINGIFY,this is used basically to create functions?I am confused how to do it.

    #define STRINGIFY(x) #x

    #define FUNC_CALL_1(x) func_call1_##x
    #define FUNC_CALL_2(x) func_call2_##x
    #define FUNC_CALL_1_F1 FUNC_CALL_1(f1)
    #define FUNC_CALL_2_F1 FUNC_CALL_2(f1)
    #define FUNC_CALL_1_F2 FUNC_CALL_1(f2)
    #define FUNC_CALL_2_F2 FUNC_CALL_2(f2)