Trick play

A trick play, also known as a gadget play, gimmick play or trickeration, is a play in American football that uses deception and unorthodox tactics to fool the opposing team. A trick play is often risky, offering the potential for a large gain or a touchdown if it is successful, but with the chance of a significant loss of yards or a turnover if not. Trick plays are rarely used not only because of the riskiness, but to also maintain the element of surprise for when they are used.

Trick plays take advantage of the fact that nearly all American football plays are either a pass from the quarterback or a run by the halfback. As a result, defenses will think pass when the quarterback has the ball and run when the running back has it. They respond by quickly changing position in an attempt to block further motion of the offense's players. Trick plays depart from these expectations, attempting to have the defense move into position to block the wrong play. They tend only to work if they are unanticipated.

In most conventional forms of American football, the quarterback receives the ball during the snap and then either throws it or hands it off to another player. That player, the "receiver", attempts to move the ball forward past the line of scrimmage. If they are successful, the line moves forward to that point and the process continues through a series of "plays", eventually (ideally) to a touchdown.

Due to a variety of interacting rules, offensive plays generally fall into two distinct groups. Plays where the (planned) source of gains are through the quarterback throwing the ball forward are known as "passing plays", while those where the gains are due to the player running with the ball are "rushing plays". Rules governing which players are eligible to receive a pass results in the offensive team being split into groups; the guards protect the quarterback, wide receivers and tight-ends are positioned at the line to run forward to receive passes, and the backs are positioned behind the line to receive the ball in a hand-off and then continue running forward for a rush.

...
Wikipedia