The foundation of a football offense is five linemen and a quarterback (QB) who lines up behind the center.  Offensive coaches vary the number of players at the running back (RB), wide receiver (WR), and tight end (TE) positions.  Here are a few of the basic formations and how they are changed from play to play.

This basic formation uses two WRs, two RBs, and one TE.  It gets its name from the two running backs (in this case the fullback and the halfback) lined up behind the quarterback, one behind the other, resembling an “I” dotted by the QB.  The WRs are split out wide with one on the line of scrimmage and one slightly behind the line of scrimmage, and the TE is next to a tackle.  The side with the TE is called the strong side with the opposite side being the weak side.

Some common variations of the I-Formation include offsetting the running back (usually the fullback) closest to the QB to either the strong or weak side and replacing one of the WRs with a second TE on the offensive line.

The basic Pro Set formation uses the same players as the I-Formation.  The primary difference is how the running backs line up behind the QB.  In the Pro Set, the RBs line up in a split backs formation, meaning one to each side of, and behind the QB.  A common variation of the Pro Set is to replace one of the WRs with a second TE on the offensive line.

The single back, as its name implies, uses one running back positioned behind the QB.  This running back can either be a fullback or a halfback depending on the situation.  A fullback is usually a heavier, stronger player who can carry the ball successfully when only a few yard’s gain is needed.  The halfback is a lighter, quicker, faster player who can avoid tacklers and run quickly to either side of the line.  The halfback looks to break through the defense for a big gain.  The running back can line up directly behind the QB or offset to either side.  The role vacated by the second running back can now be used in several capacities making this a versatile and popular formation.

Some common variations of the Single-back formations are two WRs split wide with two TEs on each side of the line, or three WRs with one in “the slot” between the tackle and the WR, or one TE, four WRs and no TEs, or five WRs, no TEs and no RBs, also known as the empty set or empty backfield.  A formation with many receivers is used in long-yardage situations.

The most notable feature of the Shotgun Formation is where the QB lines up.  Rather than directly behind the center, the QB positions himself about five yards behind the line, thus requiring the center to snap the ball a little bit further.  The extra space gives the QB extra time to throw the ball and gives receivers additional time to run their routes.  Any of the previous skill position packages can be deployed from the Shotgun Formation, but as it’s designed for passing, it usually makes use of more receivers.

Winning teams use a variety of offensive formations depending on the game situation.  Sometimes an offense will come to the line of scrimmage in one formation, but then quickly change formations to confuse the defense.