A returner is a player on the special teams who performs returns. There are a few types of returners:
The punt returner is responsible for catching the punt and ensure that his team has maintained a good field position. This is the player who determines if his team should try for a run- and this decision is made in an instant while the ball is still in the air. The punt returner's eyes must dart around the field while he successfully gets under the ball to catch it.
The kickoff returner is the player responsible for successfully catching the opposing team's kickoff. After he catches it, he must run to the opposite side of the field in attempts to score a touchdown. If the returner is able to do this, that is considered a huge feat, since there is an entire football field of defenders in his way. Any yards that the returner can gain is considered a gain for the team and sets them up a few successful downs.
On a return, the returner's responsibilities are:
A return is when a returner catches the ball from a kickoff or punt and runs with it on the field toward the opposing team's end zone. The return determines the initial scrimmage line for the offensive drive.
On a touchdown return, the returner scores a touchdown when making the return on a kickoff or punt. Touchdown returns are very rare and hard to do.
A fair catch is a signal the returner can make while the ball is in flight on a return to ask for an unhindered attempt at catching the ball. This is a very safe option, because the defenders cannot make contact with the returner, which avoids any injury. It also minimizes the chances of fumbles occurring.
A touchback is a signal the returner can make in the end zone by dropping down on one knee when catching the kickoff or punt. Touchbacks place the scrimmage line on the 20-yard line. This ends the play and is very common to see in games.