depends on the property.

examples = food/drink, laundry/pressing, unpacking, could use them for all hotel requests if you wanted to, business services, etc

the property should be clear on whats included.

had a stay recently at the sheraton park tower in london on their butler floor. drinks on arrival (chose champagne), laundry/pressing offered for free, dont think unpacking, and would have taken care of any requests if i had any. only thing i needed was reservations at morton's, which quintessentially arranged. also could have brought breakfast to the room, but didnt do that.

you pay for anything thats a regular request and not included, and i think tips are common depending on how much you have them do.