Field of Play and Scoring
A rugby field is similar in shape to a football field, but slightly larger. It is 100 meters long (not including the try zone) by 70 meters wide.
The sideline is referred to as the "touch line". Parallel to the touch line is the 5 meter line. This dashed line marks the place that the front person in a lineout must stand.
At kickoff, the ball must travel over the opponent's 10 meter line.
The 22 meter line is used for 22 meter drop-outs and determining where linouts occur when the ball is kicked to touch.
Try: 5 points
To score, a player must touch the ball down in the try-zone in a controlled manner. If a player is in the try-zone and drops the ball, it does not count. A successful try results in 5 points and an attempt at a conversion kick.
Conversion Kick: 2 points
After a player has scored a try, a conversion kick may be attempted. The kick must be taken from the place where the ball was touched down.
Drop Goal: 3 points
At any point during the game, a player may attempt to drop the ball on the ground and kick it through the posts. If it is successful, the team is awarded three points.
Penalty Kicks: 3 points
If a penalty occurs and a team is awarded a penalty kick, they may attempt to place-kick the ball through the posts from the spot which the penalty occurred.
"Rugby Union has always been characterized by the notion that it is a game for all shapes and sizes.
Uniquely, each position requires a different set of physical and technical attributes and it is this diversity which makes the game so accessible to all." - World Rugby
There are 15 players on the filed and each number correlates with a specific position.
Numbers 1-8 are forwards and numbers 9-15 are backs. Forwards tend to be your larger, stronger players. They do all the work in the scrum and lineouts. Backs tend to be smaller and faster than forwards utilizing fancy footwork and ball handling skills to manipulate the defense and create open space on the field.
Sevens rugby has (as you can surmise) seven players on the field: 3 forwards and 4 backs.
Sevens is a shorter faster paced game with two 7 minute halves. As such, players in sevens rugby tend to be leaner and faster.
Mode of Play
Kickoffs occur at the beginning of the first and second half and to restart play after a team scores.
Teams try to score by running down the field with the ball. Players may not throw the ball forward. It may only be thrown backwards or laterally. Players may kick the ball forward and any teammate may run forward to catch it as long as they were behind the kicker when the ball was kicked.
Defenders try to stop forward progression by tackling the ball carrier. Once a tackle occurs and the ball carrier is on the ground, the ball carrier must release the ball and the tackler must get out of the way. If two opposing players are at the tackle, then a ruck occurs. If there is no opposing player to compete for the ball, then a player on their feet may pick up the ball to pass or run with it.
A ruck is formed if the ball is on the ground and one or more players from each team who are on their feet close around it. Players must not handle the ball in the ruck, and must use their feet to move the ball or drive over it so that it emerges at the team’s hindmost foot, at which point it can be picked up.
A maul occurs when the ball carrier is held by one or more opponents and one or more of the ball carrier’s team mates holds on (binds) as well (a maul therefore needs a minimum of three players). The ball must be off the ground.
The team in possession of the ball can attempt to gain territory by driving their opponents back towards the opponents’ goal line. The ball can then be passed backwards between players in the maul and eventually passed to a player who is not in the maul, or a player can leave the maul carrying the ball and run with it.
The scrum is a means of restarting play after a stoppage which has been caused by a minor infringement of the Laws (for example, a forward pass or knock on) or the ball becoming unplayable in a ruck or maul. The scrum serves to concentrate all the forwards and the scrum halves in one place on the field, providing the opportunity for the backs to mount an attack using the space created elsewhere.
The lineout is a means of restarting play after the ball has gone into touch (off the field of play at the side). “The lineout concentrates a selection of forwards in one place near to the touch line, so the backs have the rest of the width of the field in which to mount an attack. The key for the forwards is to win possession and distribute the ball effectively to the back line.