Their names are given due to how they line up on the field. One is always on the outside of the other. They either advance the ball up field using the wingers as decoys or pass it out to them, in which they follow the wingers down the field as support. The wings play off of the outside center and run in their support. This is not their only role.
Wings help out on defensive maneuvers, even while their team has the ball.
They also chase after the ball after it has been kicked by the fly half, so the other team can not take a quick line-out. He must make the last effort tackles on those who out whit the rest of the players. The full back must catch and kick the ball They are sometimes included in the running plays with the other backs. This is a picture of a full team and the positions.