Skiing is not one sport but a family of them, and they have almost nothing in common except snow. Alpine skiers race downhill at 130 kilometres per hour. Cross-country skiers race 50 kilometres across flat terrain. Freestyle skiers fly through the air upside down. Ski jumpers fly further than anyone. Here is how each branch of the sport works.

Alpine Skiing

Alpine skiing — downhill skiing, as most people call it — is racing down a mountain through a course marked by gates. It is divided into speed events and technical events, and there are five individual events on the Olympic programme.

Downhill is the fastest and the most dangerous. Skiers take one run down a long, steep course, reaching speeds of around 130 kilometres per hour in an aerodynamic tuck. The fastest time wins.

Super-G (super giant slalom) combines the speed of the downhill with the turning of the giant slalom. Skiers get one run, and again the fastest time wins.

Giant slalom is a technical event with widely spaced gates and two runs. The skier with the fastest combined time wins.

Slalom is the most technical event of all: the shortest course, the sharpest turns, and gates so close together that skiers are turning almost constantly. It is raced over two runs on two different courses, with the times added together.

Alpine combined mixes the two worlds: a downhill run and a slalom run. At recent Games this has been contested as a team combined, with two athletes per team — one racing the downhill, the other the slalom — and the fastest combined time winning.

Alpine skiing joined the Olympics at Garmisch-Partenkirchen in 1936. The sport is governed by the International Ski and Snowboard Federation (FIS), which also runs the World Cup circuit and the World Championships.

Cross-Country Skiing

Cross-country is the oldest form of skiing. Before it was a sport, it was how people travelled across snow-covered country, and the Olympic events still reflect that: long races over rolling terrain, using poles for momentum.

There are two techniques. In the classic technique, skiers stride inside prepared tracks. In the free technique, skiers use a faster skating stride. Different races use different techniques: sprint and mass start races are usually classic, while team sprint and interval-start races use the free technique, and the skiathlon and relay use both.

The Olympic programme includes the sprint, run over a short course of about 1.5 kilometres; the skiathlon, which combines classic and free skiing in a single race; the mass start, a marathon of 50 kilometres for men and 30 kilometres for women; the team sprint; and the relay, with teams of four. Cross-country has been on the Olympic programme since the first Winter Games at Chamonix in 1924, and it is one of the hardest endurance sports in the world — it uses every major muscle group.

Freestyle Skiing

Freestyle skiing is the youngest branch of the sport, joining the Olympics at Albertville in 1992. It has six events:

• Moguls: skiers race down a steep run covered in bumps, and perform tricks on jumps along the way.
• Aerials: skiers launch off a large jump and perform flips and twists in the air, judged on difficulty and landing.
• Ski cross: four skiers race head to head down a course of jumps and banked turns, with the first across the line advancing.
• Halfpipe: skiers perform tricks in a U-shaped snow channel, judged on height, difficulty and execution.
• Slopestyle: skiers navigate a course of jumps, rails and other obstacles, judged on creativity, style and technical ability.
• Big air: skiers launch off one enormous jump and perform a single trick, judged on height and difficulty.

Ski Jumping and Nordic Combined

Ski jumping has been at every Winter Olympics since 1924. Skiers race down an inrun, launch from the end of the jump, and fly as far as they can, with judges scoring distance and style. Nordic combined pairs ski jumping with cross-country skiing in a single event, and it is the only Winter Olympic sport without a women's event.

Scoring

Most skiing is decided by the clock: the fastest time wins. Alpine speed events use a single run, technical events add two runs together, and cross-country races are first across the line, with sprint events using heats and finals. Judged events — freestyle, halfpipe, slopestyle, big air, aerials and ski jumping — use panels of judges scoring difficulty, execution, height and landing.

Formats and Major Competitions

The Winter Olympics is skiing's biggest stage, held every four years. Between Games, the FIS World Cup circuit runs through the winter, with the Alpine World Cup the most watched series in the sport, and the FIS World Championships are held every two years.

How to Follow Skiing

If you are new to the sport, start with the downhill: one run, one clock, and speeds that make it the most thrilling minute in winter sport. Then watch a slalom, where the turns come so fast the skis barely seem to touch the snow. For the freestyle side, the big air final is the easiest to follow — one jump, one trick, and a score out of the judges' hands.