A play that occurs at the beginning of the game, after halftime, or after a scoring play by the offense to resume play. The ball is placed on a tee at the 35-yard line of the defending team, and the kicker attempts to kick it as far as possible towards the opposing team. The team that receives the ball will attempt to return it as far as possible before being tackled or pushed out of bounds in order to improve the field position for its offense. If a kickoff attempt goes into the end zone and is not returned out of it, it is called a "touchback", and the ball is placed at the 20-yard line of the receiving team. If a kickoff goes out of bounds prior to the end zone, it is awarded to the offense at its 35-yard line.
The kickoff has a lot of elements that go into it. The kicking team is trying to pin the team as far back as possible in order to improve the odds for its defense, while the receiving team wants to gain a large number of yards to shorten the field for its offense. The kicking team will have a coverage unit that tries to tackle the returner as quickly as possible. The returner is usually one of the fastest players on the team, and he will follow a blocking unit to try and weave his way towards the end zone. On a kickoff, the kicking team may try an "onside kick", which is a short kick intended to be recovered by its own team after the kick travels 10 yards. This is a high-risk, high-reward play often used only at the end of games or as a trick play to catch the other team off guard.