Touchback

In American football, a touchback is a ruling which is made and signaled by an official when the ball becomes dead on or behind a team's own goal line (i.e., in an end zone) and the opposing team gave the ball the momentum, or impetus, to travel over or across the goal line. Such impetus may be imparted by a kick, pass, fumble, or in certain instances by batting the ball. A touchback is not a play, but a result of events that may occur during a play. A touchback is the opposite of a safety with regard to impetus since a safety is scored when the defending team is responsible for the ball becoming dead on or behind its own goal line.

Examples of instances where a touchback would be awarded include when:

In standard outdoor American football, the team awarded the touchback receives possession of the ball at its own 25-yard line in college football, and the 20 yard-line for professional football, on kickoffs and free kicks after a safety as of the 2012 season. In arena football, and other indoor football games, a touchback results in the team awarded the touchback receiving the football at its own 3-yard line. This can result from any of the above events except for punting, which is not a part of arena football. (In arena football, a kicked ball usually bounces back into play off of the rebound nets, but the above can still occur when the ball lands in the slack nets behind the goalposts after a kickoff, passes under the rebound nets and out of play, or in the event of fumbles and interceptions.)

On March 23, 2016, the NFL announced that it would award a touchback line at the 25-yard line instead of the previous 20-yard line and much discussion and analysis on the impact of this change has emerged. This new rule will be re-evaluated after the 2016 NFL season.

In college football, if a defensive player gains possession of the ball during a play between his own five-yard line and goal line and the player's original momentum carries him into the end zone, there is no touchback. Instead, the ball is dead at the point where possession changed. In the National Football League, this rule applies regardless of whether possession is gained inside the five-yard line.

...
Wikipedia