The pistol formation in football is an offensive formation where the quarterback lines up about three yards behind the center instead of directly behind in a single back formation or five yards behind in a shotgun formation. There is also a single running back directly behind the quarterback as there is in a single back formation. This hybrid between shotgun and single back formations arguably makes pistol one of the most effective and versatile formations in football.
The pistol formation's main advantage lies in its versatility that comes from its hybrid design. Having the quarterback three yards deep allows him to make downfield reads separate himself from the pass rush by a few yards. Having the halfback five yards deep and directly behind the quarterback allows him to build momentum before taking a handoff.
Additionally, the pistol's alignment strongly supports read option plays. The formation can have a fully functional pass play, keeping the halfback in to mitigate the pass rush. It can also fully commit to a run play complete with man blocking and pulling linemen.
The real nightmare for defenses, however, is the offense's ability to utilize a run pass option offense. In this scheme, plays are not written as passes or runs. Instead, the quarterback watches the defense to decide which play will see the most success. For example, the tight end may run a slant route while the running back comes down to take a handoff. If the linebackers come down to anticipate run, the quarterback would pull the ball and throw the slant. If the linebackers hold off to cover the tight end, then the quarterback hands the ball off.
Because the pistol formation is so dependent upon the quarterback being able to quickly analyze defenses and make smart decisions, it comes with a steep learning curve for the position.
Additionally, when a defense plays a solid man coverage on the receivers, it takes away most if not all of the passing game, leaving little for the offense to employ other than play action passes. The passing game out of pistol can suffer the same hits with the loss of a receiver due to injury, but of course this could be said for nearly any formation.
Ultimately, a solid pistol offense doesn't have many weaknesses or disadvantages. That's why it is so prevalent in today's college and professional settings. Teams with dual threat quarterbacks like Lamar Jackson and Colin Kaepernick particularly thrived in pistol formation, and with the large focus on passing offenses, pistol formation will undoubtedly continue to excel as it is refined.