On offense it would be the players that play on the offensive line (positions: tackle, guard, and center) and on defense it would be the players that play on the defensive line (positions: tackle and end). These positions are the ones closest to the ball when it is put into play.
In the NFL there are very few players who play two positions. Typically, if they do it is either on offense or defense and then possibly a special teams position.
Each NFL team has 53 players plus the five extra for a practice squad, there are 1,696 players in the NFL. There are 32 teams in the NFL.
53 players per team 32 teams in nfl 1696 players total
college teams with really good players will be drafted into the nfl through scouters from teams who need back ups for there starters those players soon may get drafted into the nfl
NFL teams can carry rosters of 53 players.
Some get paid millions depending how popular they are or how good they are.