The sport of freestyle skiing was invented in the 1930s, when Norwegian skiers started performing tricks and acrobatics during alpine and cross-country training. Freestyle was officially recognised as a sport by the International Ski Federation (FIS) in 1979 and the first World Championships were held in Tignes, France in 1986. Mogul skiing was added to the Winter Olympics programme for the 1992 Albertville Games and aerials were included for the first time at the 1994 Lillehammer Games.

There are two main branches of freestyle skiing. One encompasses the more traditional events of moguls and aerials while the newer branch, which is also referred to as 'new school', includes disciplines such as ski cross, half-pipe, big air and slopestyle.

Mogul skiing is a discipline in which competitors perform turns around large bumps (or 'moguls', as they called) on an extremely steep slope, with two jumps in between. Participants are judged on quality of turns (50%), speed (25%) and height and difficulty of air (25%). The best mogul skiers, who race down the fall line at frightening speeds, spin off the jumps to try and gain maximum marks, which means that they are often unable to see their landing. Though speed is certainly a factor, the fastest skier is not necessarily the winner.

Aerial skiing is a freestyle technique that involves skiing off jumps up to 15 metres into the air and then performing multiple twists and somersaults before landing on a steeply inclined landing about 30 metres in length. The leading male aerial competitors regularly perform triple back flips with up to five twists. Participants are judged on take-off (20%), jump form (50%) and landing (30%). A degree of difficulty is then factored in for an overall score.

More downhill than freestyle, ski cross is an adrenalin-filled contact race in which four, or occasionally six, skiers compete against each other on a specially designed course that is packed with various features, including slalom turns, raised banked turns, rollers, moguls and many large jumps. The winner is the one who crosses the line first.

A half-pipe, which roughly resembles the bottom half of a cylinder, is about 100 metres long and has walls up to six metres high. Skiers launch themselves off the side of the half-pipe before performing an array of somersaults, spins and grabs. Typically, a competitor can usually manage to complete five or six jumps (or 'hits', as they are known) in a run. Half-pipe exponents often use twin-tip skis, which are turned up at both ends to allow regular (forwards) and switch (backwards) skiing. Elite competitors are able to land and ski into their next hit while going backwards.

Big air is a discipline in which competitors fly off a more gentle slope than in the aerials event and perform combinations of somersaults, spins and grabs. By virtue of employing twin-tip skis, big air competitors can choose to take off or land either forwards or backwards. A panel of judges awards marks for air, style and landing, while a degree of difficulty multiplier is also factored in.

In slopestyle, a competitor is free to select his or her own route down a course consisting of various terrain features such as bumps, rails and jumps. Judges determine the winner based on the degree of difficulty and the execution of each trick.

Freestyle aerialists use many of the same moves that are employed by gymnasts and make regular use of trampolines, as well as other acrobatic or gymnastic training apparatuses, to hone their techniques. Freestyle ski jumps are perfected by skiing down specially designed ramps into large pools of water. A burst of air is sent up from the bottom of the pool just before landing to break up the surface area of the water and thereby soften the impact of landing.

Urban skiing - or 'jibbing', as it is also known - is a form of new-school skiing that is undertaken in urban areas. It includes wall rides and drops off stairs or buildings as well as skiing down handrails. It can, perhaps unsurprisingly, create trouble with authorities, but most urban skiers view their sport as an art form. They also appear to have their own language. "Man, I totally lovelled that rail" means that someone has landed on a rail incorrectly and, quite possibly, extremely painfully. Watch where you're walking when you are in an urban area!

More than 30 countries have developed active competitive programmes for freestyle skiing. Elite national teams compete annually on the FIS World Cup tour, which features events in Europe, USA, Canada, Australia, China and Japan. Ski cross and half-pipe were added to the World Cup circuit in 2004 while ski cross will be an Olympic event for the first time in 2010. Half-pipe is due to be added to the Olympic roster for the 2014 Games.

The United States have won 10 medals in freestyle skiing events at the Winter Olympics, more than any other country. Norway, Canada and France have each collected six while Finland have claimed four. Great Britain, for their part, have yet to win a medal of any colour.

When Tae Satoya won the women's moguls title at the 1998 Winter Olympics in Nagano, she became the first Japanese woman to win a gold medal at a Winter Olympics.