Hi KC,
It is checking if an specific Switch is on, which is usually activated via Business Function. Have a look at the Switch Framework doco/blogs/wiki. Here are some:
SAP Library - Switch Framework
The Three Use Cases of the Enhancement- and Switch-Framework - Part 5: The Basics about Switching
The new Enhancement Framework and the new kernel-based BAdI - ABAP Development - SCN Wiki
Cheers,
Custodio