The backfield is the area of an American football

American football

American football is a sport played between two teams of eleven with the objective of scoring points by advancing the ball into the opposing team's end zone. Known in the United States simply as football, it may also be referred to informally as gridiron football. The ball can be advanced by...

 field behind the line of scrimmage

Line of scrimmage

In American and Canadian football a line of scrimmage is an imaginary transverse line beyond which a team cannot cross until the next play has begun...

. The backfield or offensive backfield can also refer to members of offense who begin plays

Play from scrimmage

A play from scrimmage is the activity of the games of Canadian football and American football during which one team tries to advance the ball or to score, and the other team tries to stop them or take the ball away. Once a play is over, and before the next play starts, the football is considered...

 behind the line, typically including any backs on the field, such as the quarterback

Quarterback

Quarterback is a position in American and Canadian football. Quarterbacks are members of the offensive team and line up directly behind the offensive line...

, running back

Running back

A running back is a gridiron football position, who is typically lined up in the offensive backfield. The primary roles of a running back are to receive handoffs from the quarterback for a rushing play, to catch passes from out of the backfield, and to block.There are usually one or two running...

, and/or fullback

Fullback (American football)

A fullback is a position in the offensive backfield in American and Canadian football, and is one of the two running back positions along with the halfback...

.

Play in the backfield

There are many rules which differ for play in the backfield as opposed to play in front of the line of scrimmage. A forward pass

Forward pass

In several forms of football a forward pass is when the ball is thrown in the direction that the offensive team is trying to move, towards the defensive team's goal line...

 can only be legally made from the backfield. Most running plays begin with a handoff in the backfield.

If the offensive ball-carrier is tackled

Tackle (football move)

Most forms of football have a move known as a tackle. The primary purposes of tackling is to disposses an opponent of the ball, to stop the player from gaining ground towards goal or to stop them from carrying out what they intend....

 in the backfield, the team will lose yards, in that the distance they need to attain for a first down is more than at the beginning of the play.