Each NFL team consists of a 46-man game day roster; however, each team carries 53 men on their active roster. This means that seven players are on the roster but do not dress for the game on that particular week. During an individual play, 22 players will be on the field at each time: 11 for the offense and 11 for the defense.
There are many combinations teams may use during the game in terms of roster based on their gameplan. On offense, teams will typically have at least five offensive linemen at any individual time and one quarterback. Depending on the situation, the team will include combinations of tight ends, running backs and wide receivers. The offense can strengthen an aspect of their offensive game by adding or subtracting players from those positions. For example, in a 3rd and long situation, a team may elect to use five receivers and no running backs in what is called an empty backfield.
The team on defense will often have a combination of defensive linemen, linebackers, and members of its secondary (free safety, strong safety, cornerbacks) often matching up with the way the offense lines up on the field. This changes based on different types of defenses that are run, for example, a 4-3 defense consists of 4 defensive linemen and 3 linebackers.
Typically, NFL teams keep two quarterbacks, four running backs, three tight ends and nine offensive lineman on offense, as well as nine defensive lineman, seven linebackers, and 10 defensive backs on the defensive side. This can change based on a team's strengths and weaknesses as they may add to positions of weakness while subtracting from positions of strength.