Include program!

Dear SDNers,

How can i find an include program (user exit) for a particular t-code.

Say suppose, in t-code VA01 we have lot of exits and also we have include program MV45AFZZ to do user modifications.

Could anybody tell me what is the exact difference between this exit and include program? why they are providing these two types?

FYI, I have the program for finding the user exit for a particular t-code.is there any other program for finding the includes?

Appreciate SDNers prompt response.

Senthil kumar 😊