In rugby football, the offside rule prohibits players from gaining an advantage from being too far forward.
However the basic principle is simple: a player may not derive any advantage from being in front of the ball.
In particular, a player in an offside position[1] Infringement of any of these rules is generally punished with a penalty awarded to the opposing team.
They may move closer only to catch a long throw-in, or after the line-out ends, when the ball or a player carrying it leaves the lineout in any direction.
If not, he must stand 10 metres away from the player who catches the ball (as if he were the acting half-back at a play-the-ball) or be penalised.