The NFL is the National Football League, a professional American football league. The three positions mentioned in the crossword solutions are END, CTR, and LINEMAN. An END is a wide receiver or tight END, who lines up at the END of the line of scrimmage and is responsible for catching passes from the quarterback. CTR stands for center, who is the player who snaps the ball to the quarterback to start each play. Lastly, a LINEMAN is an offensive or defensive player who lines up on the line of scrimmage and is responsible for blocking and tackling.