What is "two-point conversion"

n. (context American football English) An option, for a team that has scored a touchdown, to gain two points by getting the ball into the end zone by a running or pass play, in lieu of a kicked extra point.

In American and Canadian football, a two-point conversion or two-point convert is a play a team attempts instead of kicking a one-point conversion immediately after it scores a touchdown. In a two-point conversion attempt, the team that just scored must run a play from close to the opponent's goal line (5-yard line in amateur Canadian, 3-yard line in professional Canadian, 3-yard line in amateur American, 2-yard line in professional American) and advance the ball across the goal line in the same manner as if they were scoring a touchdown. If the team succeeds, it earns two additional points on top of the six points for the touchdown. If the team fails, no additional points are scored. In either case, the team proceeds to a kickoff.

Various sources estimate the success rate of a two-point conversion to be between 40% and 55%, significantly lower than that of the extra point, though if the higher value is to be believed, a higher expected value is achieved through the two-point conversion than the extra point.