ROSTER SIZES
Active ("Gameday") list: If a team has a minimum of eight offensive linemen (primary position being center, guard or offensive tackle) on the active game day roster, the maximum roster size is 48 players. If a team has fewer than eight offensive linemen, the maximum drops to 47 players.
Active/inactive ("53-Man") list: The active/inactive list remains at 53 players for the regular season and playoffs. However, a team can increase its roster to 54 or 55 players only by using the standard elevation addendum (explained below) to bring one or two practice squad players to the active/inactive list.
Roster size: The practice squad consists of 12 players in 2021, before increasing to 14 players beginning in 2022.
Standard elevation addendum: Now included in all practice squad contracts, the standard elevation addendum allows teams to move a player from the practice squad to the active/inactive list for one week and then back to the practice squad without subjecting him to waivers. Under this addendum, a player reverts back to his team's practice squad on the first business day after the game in which he is elevated. These players receive the applicable minimum salary for a player with his number of credited seasons (prorated for one week of regular season pay or the applicable postseason amount). This clause can be used by a team for a maximum of two regular-season or postseason games per player per season. If the team elevates a player for a third time and the team wishes to move him back to the practice squad, it has to waive or terminate his player contract. If a player is released or clears waivers (whichever is applicable) and he signs a practice squad contract with a new team, he is once again eligible to be elevated for the aforementioned maximum of two games.
https://www.nfl.com/news/2021-nfl-free-agency-glossary-all-the-terms-you-need-to-know