A touchdown is a means of scoring in American and Canadian football. Whether running, passing, returning a kickoff or punt, or recovering a turnover, a team scores a touchdown by advancing the ball into the opponent's end zone.
To score a touchdown, one team must take the football into the opposite end zone. The touchdown is scored the instant the ball crosses the plane of the goal line. That is, if any part of the ball is in the space on, above, or across the goal line, while in possession of a player whose team is trying to score in that end zone. The play is dead and the touchdown scores the moment the ball crosses the goal line in possession of a player, or the moment the ball comes into possession of an offensive player in the end zone, having established possession by controlling the ball and having one or both feet or another part of the body on the ground. The slightest part of the ball being over the goal line is sufficient for a touchdown to score. However only the ball, not a player's helmet, foot, or other part of the body, counts. Touching one of the pylons at either end of the goal line with the ball constitutes "breaking the plane" as well.
A touchdown is worth six points. The scoring team is also awarded the opportunity for an extra point or a two-point conversion. Afterwards, the team that scored the touchdown kicks off to the opposing team, if there is any time left.