There are four ways to score points in football, each with their own value.
Touchdown (six points): This is the biggest way to score and is when the offensive team gets the ball inside the defensive team's end zone, located at the end of the field.
Extra point (one or two points): After a touchdown, the offense has a chance to score an extra point by kicking the ball through the goal posts from the 15-yard line. They can also choose to try for two points instead, called the two-point conversion, by trying to run or throw the ball into the end zone. A two-point conversion is attempted from the two-yard line.
Field goal (three points): If the offensive team has made it a good way down the field but won't be able to make another first down or reach the end zone for a touchdown before having to give up the ball, they can try for a field goal, which is when they kick the ball through the goal posts just like they do for an extra point. Where the ball is kicked from on the field depends on where it was stopped — it can be close or far depending on how much the team has advanced up the field.
Safety (two points): This is less common, but usually happens when someone on the offense who is in possession of the ball is tackled in their own end zone.
