After a touchdown, a 'try' occurs. The try consists of the offensive team performing a play after the touchdown for either one or two points. Teams can either perform an extra point attempt, called the point after touchdown (PAT), or a two point conversion.
The PAT works in the same way as a field goal in which the ball is snapped to a holder and the ball is kicked through the upright goal posts in the end zone. The PAT is worth one point and the ball is kicked from the 15 yard line.
Teams can also attempt a two point conversion in which the ball is placed on the two yard line and the offensive team must get the ball across the goal line like scoring a touchdown. The two point conversion is worth two points and the offensive team only gets one chance to get the ball across the goal line for a successful conversion (unless there is a penalty of some kind in which a replay of down is required).
After the try has concluded, a kickoff will take place in which the previous offensive team will kick-off to the opposing team. The ball is kicked from the 35 yard line and the possession will change over from the team that scored to their opponent.
In football after each scoring play, a review occurs. The referees look at instant replay monitors of the play to confirm whether or not the play should be called a touchdown. In the event they decide the play should not be a touchdown, the offensive team comes back out onto the field to continue play.