How does the IL carry and conceal law work?

I was thinking about applying for my carry and conceal license, but not sure how IL defines carry and conceal.

Can the gun holster be exposed, or does the holster have to be hidden in public view. I know that if you live in Indiana, the gun holster does not have to be hidden from public view. You can walk into any grocery store, gun show, firework store, and gas station and see who is carrying a gun. I'm a little confused because you don't see anyone carrying a gun holster in IL. Can the gun holster be exposed or not. Any help would be appreciated.