Concept Artists– Usually draw 2D images environment or character passed onto production. Responsible for keeping continuity, if art is good, more chance of real game to be good. (Take note of how artists present work).
3D Artists– Working day consists of sculpting objects, characters in 3D changing high poly to low.
Technical Artist- Only some studios will have one as it is usually just part of the art and programming team. Shader programming and shader optimisation is a main part of the role.
Animator- Most often applied to give life to a game. Also applied to elements like trees and flags, not just characters. Blending animation to character controls seamlessly.