The actor class encapsulate almost any unreal entity that you can place in the world. So in your case, the mechanic, the environment and the machine are all actors. A pawn is a particular actor that can be possessed and controlled either by a player or an AI (something that has a “brain”). In your case, the mechanic which is controlled by the player is the pawn. And finally the character is a particular pawn that, simply put, has built-in humanoid features, like walking, jumping and interacting with the world.
I’m just confusing for the understanding of UE4 terms, For example; I want to make a game like a car mechanic so I must have a workshop environment for it. So is this an actor or something? Another issue I want to place a machine into this workshop environment and player should interact with this machine, and the machine should have complex movements, animations. So my question is which is the actor , which is spawn, which is a character in this case. I mixed all of them