What does AddRoll/Ptich/YawInput does?

I am asking in terms of logic not the code. what does AddRollInput, AddPitchInput or AddYawInput does in context of a player controller and pawn? does it only updates the rotator values of the PlayerControllerActor or actually rotates it?

If you don’t have your pwan set to take rotation from player controller then how do you make only certain components of the pawn take the rotation from the controller? What happens to the rotation default camera if I use camera component from the pawn actor?

What is the purpose of the parameter value?