According to Newton's third law, for every action, there is an equal and opposite reaction. The action and reaction forces act on different bodies. For example, if a ball is thrown to a wall. The ball applies an action force on the wall, in return the wall applies the reaction force on the ball. Hence, the action force acted on the wall but the reaction force acted on the ball.
Action and reaction forces are equal in magnitude but opposite in direction. Yes, they are simultaneous in nature as they are applied at the same instant but on different bodies.