Powers: Powerful telepath and he can control thoughts. That means he can read your mind and make you do whatever he wants.
Past: You do not learn anything about his past from the movie.
Introduction into movie: He is teaching a class when Logan runs into his office, trying to hide from something.
Importance to the movie: He is the one whom created the "School For Gifted Youngsters." So he's pretty important if you ask me!