What does C mean in football?

C is a center in football. The lineman who snaps the ball and sets the line’s protection calls before it.

What a center looks like

81 centers are on NFL rosters right now, and the median one is 6' 4" and 306 lb.

On rosters
81
Median height
6' 4"
Median weight
306 lb
Median age
26

The centre makes the line’s pre-snap calls, so clubs treat him as a second quarterback of the front five; none of that is counted either.

The rest of the NFL roster