(Source: Wikipedia)

Australian football, also known as Australian rules football or less formally as "Aussie rules" or simply as "footy", is a code of football that originated in Melbourne, Australia. The game is played between two teams of 18 players (plus interchange players) on cricket ovals or similar-sized grassed arenas that vary in size and may be up to 185 metres (200 yards) long; these are much larger (almost four times the area) than those used by other codes of football.

The game is also distinguished from other games by the fast, relatively free, movement of the ball (partly due to the absence of an offside rule) and the awarding of a free kick for any mark (clean catch) of a ball that has been kicked more than 15 metres. Spectacular high marks or "speccies", tackles and fast fluid play are the game's main attributes as a spectator sport.

Although it is a winter sport, pre-season competitions usually begin in late February (late summer in the southern hemisphere). The football season, proper, is from March (early autumn) to August (late winter) with finals being held in September (early spring).  In the UK we play the game in the same months, but during our summer.

Both the ball and the field of play are oval in shape. No more than 18 players of each team are permitted to be on the field at any time. Up to four interchange (reserve) players may be swapped for those on the field at any time during the game. There is no offside rule nor are there set positions in the rules—unlike many other forms of football—players from both teams disperse across the whole field before the start of play.

The ball can be propelled in any direction by way of a foot, clenched fist (called a handball or handpass) or open-hand tap (unlike rugby football there is no knock-on rule) but it cannot be thrown under any circumstances. Throwing is defined in the rules quite broadly but is essentially any open hand disposal that causes the ball to move upward in the air.

A player may run with the ball but it must be bounced or touched on the ground at least every 15 metres (throwing down to bounce it is allowed). Opposition players may bump or tackle the player to obtain the ball and, when tackled, the player must dispose of the ball cleanly or risk being penalised for holding the ball.

If a player takes possession of the ball that has travelled more than 15 metres from another player's kick, by way of a catch, it is claimed as a mark and that player may then have a free kick (meaning that that the game stops while he prepares to kick from the point at which he marked). There are different styles of kicking depending on how the ball is held in the hand of which punt (the ball is held about or below the waist and the foot comes up to it) or drop punt (the ball is thrown forward and down, almost to the ground, to be kicked) are two.

Apart from free kicks or when the ball is in the possession of an umpire for a ball up or throw in the ball is always in dispute and any player from either side can take possession of the ball.

Scoring
At each end of the field are four vertical posts. The middle two are the goal posts and the two on either side, which are shorter, are the behind posts, or point posts.

A goal is scored when the football is propelled through the goal posts at any height (including above the height of the posts) by way of a kick from the attacking team. It may fly through on the full or bounce through and must not be touched, on the way, by any player from either team. A goal cannot be scored from the foot of an opposition (defending) player.

A behind is scored when the ball goes across the line between a goal post and a behind post or if the ball hits a goal post or if it is touched (a rushed behind) before passing between the goal posts.

A goal is worth 6 points whereas a behind is worth 1 point.
The team that scores the most points at the end of play wins the game. A score of 10 goals and 10 behinds equals 70 points. A score of 9 goals and 18 behinds equals 72 points.

Similarities to Gaelic football

While it is clear even to casual observers that Australian rules football is similar to Gaelic football, the exact relationship is unclear, as the Irish game was not codified by the Gaelic Athletic Association (GAA) until 1887. The historian B. W. O'Dwyer points out that Australian football has always been differentiated from rugby football by having no limitation on ball or player movement (in the absence of an offside rule), the need to bounce the ball (or toe-kick it, known as a solo in Gaelic football) while running, punching the ball (hand-passing) rather than throwing it, and other traditions. As O'Dwyer says:
These are all elements of Irish football. There were several variations of Irish football in existence, normally without the benefit of rulebooks, but the central tradition in Ireland was in the direction of the relatively new game [i.e. rugby]...adapted and shaped within the perimeters of the ancient Irish game of hurling... [These rules] later became embedded in Gaelic football. Their presence in Victorian football may be accounted for in terms of a formative influence being exerted by men familiar with and no doubt playing the Irish game. It is not that they were introduced into the game from that motive [i.e. emulating Irish games]; it was rather a case of particular needs being met... [B. W. O'Dwyer, March 1989, "The Shaping of Victorian Rules Football", Victorian Historical Journal, v.60, no.1.]

After 1887, the two games developed in isolation from each other. A number of players, most notably Jim Stynes have successfully made the transition from Gaelic football to Australian rules.