American football involves a great deal of strategy and execution. There are many different alignments and plays that can be run in many different situations. For example, there are kickoffs, field goals, and punts which all require different alignments, as well as standard offensive and defensive alignments that vary widely.
See American football for a description of positions used. There are literally hundreds of offensive alignments that are commonly used in the game of football, although most are slight variations on a theme, or a set of personnel. All offensive formations use 5 offensive linemen who are not allowed to handle the ball, and 6 "skill" position players who are allowed to handle the ball. Exactly 7 players must always be on the line of scrimmage when the play begins. This article will organise offensive alignments by the personnel that are on the field, and assumes that a quarterback is used in every formation.
One of the most basic offensive alignments is the I formation. The quarterback aligns directly behind the center, the fullback several yards behind the quarterback, and the halfback several yards behind the fullback. The tight end aligns directly next to the furthest offensive lineman, usually on the right side, and 2 wide receivers are split several yards to the outside of the offensive line.
This formation is a fairly balanced alignment. It slightly favours a power running game, as the offensive line, fullback, and tight end are able to block opposing defensive players, it is versatile enough to allow runs to many different areas of the middle of the field, as well as off-tackle and even some sweep and pitch plays. The I-formation is also fairly good for passing plays, especially using play-action, where the offense fakes a running play before passing.
There are several possible variations of the I formation. The fullback may align slightly to the left or right, usually called a weak or strong I respectively. Also, both wide receivers can line up on the same side, rather than different sides.
In a split back formation, the running backs are behind the quarterback and each is split to one side. It is somewhat more common to have the halfback on the right (tight end) side, but he is also sometimes aligned to the left. The tight end lines up next to an offensive tackle, usually on the right side, and the wide receivers are aligned to the outside. The quarterback takes the snap directly under center.
The split back formation is more of a finesse formation. It allows off-tackle runs, sweeps, and pitches, and gives the running backs more space to act as receivers. It is possible to run up the middle, but less effective because the fullback is not stacked in front of the halfback as in the I, making it difficult for him to act as a lead blocker. Many running plays use "trap-blocking" whereby an offensive lineman moves to the outside to act as a lead blocker, while the fullback blocks a defensive lineman in the area he came from. The formation is usually quite effective for passing, as the wide receivers, tight end and possible one running back can act as receivers, while one running back stays back to protect the quarterback.
The Near formation involves a halfback aligned several yards directly behind the quarterback, with the fullback aligned to his right in the backfield. In the Far formation, the fullback instead aligns to the left of the halfback. This formation lends itself more to off-tackle and outside runs, rather than running up the middle.
This is a shotgun formation, meaning the quarterback begins several yards behind his center, and the ball is snapped in the air to him. The running backs are on either side of the quarterback, usually with the halfback on the left side. The tight end may split out, or move several yards away from the offensive line and begin from a standing position, rather than with a hand on the ground, in order to give him more space to act as a receiver.
A singleback big formation has 1 running back who is aligned several yards directly behind the quarterback. There are two tight ends, usually one on each end of the line, and 2 wide receivers who are split out. Sometimes both tight ends are on the line of scrimmage, while sometimes one may be just behind the line of scrimmage, in an alignment called an "h-back".
This is considered more of a power running formation, as it has two tight ends to block. It is very good for off-tackle runs, and runs to the outside, although it typically is not as good as an I formation for runs up the middle. In the passing game, usually either a tight end or the running back will help protect the quarterback, while the other players attempt to get open.
The Spread offense has 5 wide receivers and one quarterback, who lines up directly behind the center. With no running back, this is almost exclusively a passing formation, although a quarterback may run draw plays, or scramble if no one is open. The formation is fairly flexible; it allows deep passes, although it tends to focus on medium and shorter range passing, as it is difficult to protect the quarterback with only the offensive line. There are also many screen passes that are available to the wide receivers.
A Shotgun 5 wide receiver set is exactly like a Spread offense, except that the quarterback begins several yards behind the center, and receives a shotgun snap. This formation is typically used in "Hail-Mary" situations, where a team must score in a single play from a long distance.