[1] Teams use personnel groupings in order to set a base for most of their plays, as well as being able to send out players in a timely manner during a game.
The groupings used in different formations can vary depending on what the coach and offense want to do, but there are generally different types of personnel used for either a running or passing play.
The goal is to create favorable match-ups and force the defense to adjust and react while controlling the clock.
Usually, personnel groupings are differentiated using a numerical system to set apart the running backs, tight ends, and wide receivers.
[6] The NFL and the sport itself are always changing and teams are constantly trying to gain a competitive advantage by adapting and executing new concepts.