A tight end is an offensive position in American football that works as either an extra blocker or an extra receiver on a given play. Tight ends typically have both receiver and lineman attributes, and some teams use them more heavily in one position or the other.
Most teams have tight ends that specialize more in blocking as well as those that specialize in receiving. In that case, the coach can decide to put the blocking tight end in for a running play, or a receiving tight end in for a passing play. An offensive formation can contain as many as three tight ends or as little as zero tight ends at one time.
Tight ends either take a position on or off the line of scrimmage depending on the play. On the line of scrimmage, the tight end is available to block either a defensive end or linebackers coming off the edge. Usually his job is to clear up space on the edge for a running play. However, it is also possible for him to be motioned into the slot by a quarterback calling an audible. Tight ends may also block on passing plays off the line of scrimmage, but often roam uncovered into the slot, allowing the quarterback to get them the ball in space.