Unreal's "Actor" is a "thing that can be placed in a level" - it then has "Pawn", which is a "controllable actor". It also has the concept of a "Controller" class on an Actor - the purpose of the controller is manipulate the Pawn. This ends up in essentially "PlayerController" and "AIController", with the former taking input from humans and the latter taking input from the AI subsystems. The idea is that characters (pawns) can be controlled by either Players or AI by swapping out the controller.
In UE, Player input is handled by an input system translating the raw platform input into a series of 'actions' (eg: space maps to jump, w maps to move forward, etc). These actions are handled by an InputComponent that lives on the PlayerController. This is what says "take the move forward action and actually do something with it". There's a good description on UE's InputComponent system here.