What's the basic story in the series of Mega Man X? [closed]

As a kid, I loved playing Mega Man X for the mechanics and didn't really pay attention to the story. I have been playing 20XX, and am realizing that I am unable to make any connections to the analog characters besides Nina (Mega Man) and Ace (Zero). I have vague memories of a collection of scientists, and specifically a "Dr. Light". I would like to have a basic grasp on the story and characters of the X series without having to play through the games again. Can someone provide a summary?