Difference between USEREXIT and EXIT?

Hello Experts,

I have to implement the USEREXIT_FILL_XKOMK1. But i am not able to find it in SMOD. I have already implemented the EXIT_SAPLV60B_001 user exit for this i have created the project and activate it. Do i need to create the project for USEREXIT_FILL_XKOMK1 and it will be helpful if you can tell me user exit name in SMOD.

Thanks,

Amit