Games that try to simulate real-world activities (like driving vehicles or living the life of someone else) with as much realism as possible. Simulators generally require more study and orientation than arcade games, and the best simulators are also educational.
Shoot 'Em Up or shmup games are a subset of shooter games where the player continually moves forward while waves of enemies enter the screen. Both shooting and dodging are critical to advancing. See also Bullet Hell.