OK, many different people are gonna tell you a number of different things about what you need to know about football. But here is my attempt...
Two teams are playing each other to see who scores the most amount of points. Simply put, points can be scored by way of touchdowns (where a player on one team gets the ball into the other team's end zone which is located at the ends of the field, or the team can kick a field goal, which is when one team kicks the ball through the big Y looking thing on the ends of the field. Each team has four "downs" to try to get a "first down, which means that they are given four more downs. A first down can be achieved by way of getting 10 yards or more within those four downs. Due to field positioning, where a team's offense is on the field, being an issue, on fourth down, a team will likely punt if they are on their end of the field.
Terms:
Offense
Quarterback (QB) the player that throws the ball or hands the ball to the Running Back
Running Back (RB) the player that will block the QB or carry the football towards the other team's end zone
Wide Receiver (WR) the player that will run down field on a play so that the QB can try to throw the ball to them
Offensive Linemen (OL) the players that snap the ball and try to prevent the other team's defense from getting to their QB
Defense
Defensive Linemen (DL) the players that try to get past the other teams OL so that they can tackle the quarterback or whoever has the ball
Linebackers (LB) the players that line up behind the DL and either cover WRs, tackle the RBs or run at the QB
Defensive Backs (DB) the players that play further from the "line of scrimmage", covering the WRs when they run down field and try to prevent the QB from throwing the ball too far down field.
General
Line of Scrimmage: where the ball is placed every play, and where all players have to start from, it is as close to the other team as you can be before the ball is snapped
Ball being snapped: when the OL hands the ball or throws the ball between their legs to the QB to start the play
Feel free to email me with any other questions. It is a complicated game with A LOT of strategies, so there are a lot of different things that can happen. There are also penalties, which I will explain if you call me.