A safety awards the opposing team 2 points in the NFL.
A safety occurs when the offense causes the ball to become dead in its own end zone. The most familiar example is a quarterback being tackled in the end zone, often after a sack. It can also happen when a ball carrier steps out of bounds there, a fumble goes out through the end zone, or an offensive foul is enforced in that end zone.
The points go to the defense, even though the defense does not need to carry the ball into the opponent’s end zone. Afterward, the team that conceded the safety must give the ball back with a free kick from its 20-yard line, creating an unusual change of possession.
A safety is different from a touchback: if the receiving team catches an interception or kickoff in its own end zone and is downed there, the result is normally a touchback rather than a safety. Safeties are uncommon, which is why they often produce memorable football scores.