A lineout is what happens when the ball goes out of bounds. This could happen if the ball is kicked or thrown out of bounds, or the ball carrier runs or is tackled to out of bounds. It takes place at the point where the ball or ball carrier went out of bounds.
In a lineout, the forwards form two pods of three people, two lifting and one jumping, to catch the ball being thrown in through the gap. the two pods then step in together and lift the jumper in order to catch the ball. While the jumper is in the air, she can not be tackled until she is back on the ground.
However, she wants to pass the ball to the waiting scrum half, who will them pass it to the back line, as soon as possible. This will give them more time to gain yards before meeting the other team’s defense.
The team that the lineout is to sets how many pods the lineout has, and the other team matches their numbers. The team that the lineout is to also is the one to throw the ball in, giving them the advantage of knowing how high the ball will go.