The halfback in football is a type of running back (HB) who specializes in running plays as the ball carrier. The halfback gets the ball via a hand off from the quarterback at the start of a down. Halfbacks can also serve as receivers on passing plays.
The halfback's main role is to run the ball during plays when it is handed off to him. He should be a very quick runner, and a player that is light on his feet, because he might have to adjust to different lanes opening and closing. He also should be skilled in reading the field at a glance, noting where his opponents are and where his open teammates are positioned. If the ball isn't handed off to him, he serves as an extra blocker, keeping opponents away from the ball carrier. The halfback can also serve as a receiver and catch passes if he is needed in that role during a game.