What is a Shooter‪?‬ Questin' Mark

This is the first episode of my series called Questin' Mark where I will talk about random little things that I feel annoyed by or want to get my opinion out on. This first one hit me while playing Call of Duty: Modern Warfare and it got me thinking what are FPS games and shooters in general? How are they different? What makes a game a shooter and not one? basically that's what I cover in this episode of Questin' Mark