Breakdowns
A rugby tackle: tackles must be below the neck with the aim of impeding or grounding the player with the ball
The aim of the defending side is to stop the player with the ball, either by bringing them to ground (a tackle, which is frequently followed by a ruck), or by contesting for possession with the ball-carrier on their feet (a maul). Such a circumstance is called a breakdown and each is governed by a specific law.
A player may tackle an opposing player who has the ball by holding them while bringing them to ground. Tacklers cannot tackle above the shoulder (the neck and head are out of bounds), and the tackler has to attempt to wrap their arms around the player being tackled to complete the tackle. It is illegal to push, shoulder-charge, or to trip a player using feet or legs, but hands may be used (this being referred to as a tap-tackle or ankle-tap).
Mauls occur after a player with the ball has come into contact with an opponent but the handler remains on his feet; once any combination of at least three players have bound themselves a maul has been set. A ruck is similar to the maul, but in this case the ball has gone to ground with at least three attacking players binding themselves on the ground in an attempt to secure the ball.