Rugby union is a contact sport that consists of two teams of fifteen players. The objective is to obtain more points than the opposition through scoring tries or kicking goals over eighty minutes of playing time. The play is started with one team drop-kicking the ball from the halfway line towards the opposition. The rugby ball can be moved up the field by either carrying it or kicking it. However, when passing the ball it can only be thrown laterally or backward. The opposition can stop players moving up the field by tackling them. Only players carrying the ball can be tackled and once a tackle is completed the opposition can compete for the ball. Play continues until a try is scored, the ball crosses the side line or dead-ball line, or an infringement occurs. After a team scores points, the non-scoring team restarts the game at the halfway with a drop kick toward the opposition. The team with the most points at the end wins the game.

A typical passage of rugby union takes the following form. Unlike rugby league and gridiron football, possession of the ball in rugby union is contestable at any time by both teams – there is no separate 'offense' and 'defense'. The team which has possession of the ball at any given time will normally try to keep it, while the other team will try to recapture it, or at least deny the team in possession the chance to attack and/or force it to kick the ball away or commit an error. One team will initially gain possession of the ball, either from the kick-off, a restart kick or a set piece (scrum and line-out). The need to maintain possession means the team with the ball will usually seek to progress towards the opposition by running forward while carrying the ball; although if there are few opportunities to attack they may choose to kick the ball forward, from the hand, usually giving it back to the opposition but in a position from where it will be difficult to attack. The ball may be thrown from one player to another (passing) but must not be thrown forward, that is towards the opposition dead-ball line. Any teammate ahead of the ball-carrier is offside and must not interfere with play. So American football-style blocking is forbidden, although tackling or obstructing a player who does not have the ball is against the laws anyway, whether or not the tackling player is offside. The team not in possession attempts to stop the ball-carrier by grabbing and bringing them to ground (a tackle). A tackled player, once having been brought to ground, must immediately pass or release the ball, allowing the two teams to contest possession of the loose ball; if the attacking player is tackled but the tackler releases the ball carrier the ball carrier may get up and continue the play. Play does not stop unless there is an infringement of the Laws, the ball/ball-carrier leaves the field of play, the ball becomes unplayable after a tackle, or the attacking team scores points by either touching the ball over the goal-line (a try) or drop-kicking the ball over the crossbar. If the ball or ball-carrier goes into touch (out of the field of play), the game restarts with a line-out. If the game stops due to an infringement, play restarts with either a scrum, free kick or penalty kick (depending on the nature of the infringement) to the non-infringing team.

Players can run with the ball in any direction they want. However they cannot use a teammate to obstruct the opposition. This occurs when they run around or into one of their own players and in the process prevent a defender from tackling them. Defending teams can also run anywhere they want as long as they do not start from an offside position. Offside lines are behind the last foot at a ruck, maul or tackle or five and ten metres back from scrums and lineouts respectively. If the ball is kicked, players from the kicking team cannot run forward until they have been passed by the kicker or someone behind the kicker.

Forwards tend to run straight and hard at the opposition, while the backs run at gaps between players or use speed and guile to run around them. In modern games of rugby some backs can be as big as forwards and attempt to break through the defensive line using brute force and many forwards possess the running skills of backs. Players run straight at the opposition with the aim of either breaking the tackle or getting forward momentum from which to set up another attack. If they are close to the try line they can drive in low to aid grounding the ball. Players can also try to break through tackles by spinning after making contact or by using the hand not carrying the ball to fend (push) off the defender.

A player could also try to get around a defender by stepping, swerving, or goose-stepping past them. To sidestep a defender, the attacking player takes a wide step in one direction while running forward and then shifts their body weight in the opposite direction. If successful the defender will be off balance, allowing the attacker to accelerate past. When swerving, an attacker runs straight at the defender, but before making contact accelerates and sways to the outside. Although similar to a side step, the swerve involves less sideways movement, but results in less loss of speed. The goose-step is a move made famous by David Campese and involves slowing down while running on the outside of the opponent, causing them to also slow, before accelerating away.

The ball can be passed laterally or backwards, but cannot be thrown forward. The opposing team is awarded a scrum if the ball is unintentionally thrown forward or if it is knocked forward from a player's hand or arm – although doing so deliberately results in a penalty. An exception is if a player knocks the ball forward in attempting to block an opponent's kick – a 'charge down'. Passing is an integral part of rugby union, as it allows the ball to be easily and quickly distributed to teammates. The backs are the major participants of passes, and they are used to put running players into space. If a team has an overlap – more players attacking than the other team has defending at a particular moment – then the tactic is to draw a defending player to the tackle and pass to the person outside him. If every player executes the 'draw and pass', given space, the outside players may have no defenders in front of them.

Another tactic is pretending to pass the ball, called 'dummying'. It can be used during normal backline play or as part of a set move. The aim of the dummy is to confuse the opposition and create a gap for the player carrying the ball. When used as a set move a player will run as a decoy, usually at a different angle to the rest of the players. In complicated moves there will be multiple players acting as decoys. Care must be taken to ensure the decoys do not impede the tacklers, which would result in a penalty being awarded to the defenders.

The standard rugby pass is the spiral pass, where the player swings the ball across his body with the tip point upwards and the ball spinning about its axis. This technique propels the ball quickly and accurately. 'Quick hands' is the rapid movement of the ball between players, and at its best involves catching and passing the ball in one motion. A 'skip-pass' is a basic move where the ball is passed past the closest player to another further away. The 'double-around' is another simple move that involves the passer quickly running around the player to whom he has just passed the ball and then receiving the ball back from him. If successful it can create an overlap. Another common passing move is the 'cut and switch', which is used to change the direction of the play. For a cut the ball carrier runs laterally across the field before passing the ball to a player running back on an angle; the switch is a simple change of direction: a player standing on one side of a scrum, ruck or maul receives the ball and then passes it to someone on the opposite side.