The Olympic flame and the torch relay.

Next to the Olympic Rings, the Olympic Flame is the most universally recognized symbol of the Games. For the public, the Torch Relay is often the first and most tangible evidence of the arrival of the Games.
The Olympic torch is lit several months before the start of the actual games. The flame begins its journey at the site of the original Olympic Games -- Olympia, Greece. It is lit, just as it was in ancient times, at the Temple of Hera.
An actress dressed as a ceremonial priestess, in the robes of the ancient Greeks, lights the torch via the same technique used in the original Games. She uses a parabolic mirror to focus light rays from the sun. The parabolic mirror has a curved shape. When it is held toward the sun, the curvature focuses the rays to a single point. The energy from the sun creates a great deal of heat. The priestess holds a torch in the center of the parabolic mirror, and the heat ignites the fuel in the torch, sparking a flame.
If the sun is not shining on the day of the lighting ceremony, the priestess can light the torch with a flame that was lit on the day of dress rehearsal, before the ceremony.
The flame is carried in a fire pot to an altar in the ancient Olympic stadium, where it is used to light the first runner's torch. For the Winter Games, the relay actually begins at the monument to Pierre de Coubertin (the man who founded the modern Olympic games in 1896), which is located near the stadium.
Then, the relay begins. The journey to the host city varies from year to year. The Olympic Games Organizing Committee (OCOG) determines the route, as well as the theme, modes of transportation for the torch, and the stops that it will take along its way to the Opening Ceremony.
The torch is generally carried from one country to another on a plane. Once it arrives in a city, it usually spends one day being carried from torchbearer to torchbearer on foot. It may also be ferried from place to place by car, boat, bicycle, motorcycle, dog sled, horse, or virtually any other type of conveyance.
On certain legs of the relay, the torch must be housed in a special container. For a trip across the Great Barrier Reef before the 2000 Olympic Games, a special torch was designed to burn underwater. On airplanes, where open flames are not allowed, the flame is typically stored in an enclosed lamp, much like a Miner's lamp. At night, it is kept in a special cauldron until the relay begins once again the following day.
As in any relay race, each runner carries the torch for only one short leg of its trip As a runner completes a leg, he lights the torch of the next person in the relay.
It is considered a great privilege to be chosen as a torchbearer. Athletes, actors, musicians, sports figures, and politicians have all carried the flame. In 1996, boxing legend Muhammed Ali lit the Olympic cauldron to mark the start of the Games in Atlanta. But the brunt of the running is done by average citizens all around the world.
Almost anyone can carry a torch, provided that he is at least 14 years old and is able to carry it for at least 400 meters (437 yards). Handicapped people can be (and have been) torchbearers -- they can carry the torch while riding in a wheelchair. The torchbearers are chosen by the Olympic sponsors and organizers, usually because they have made a significant contribution to their community and because they personify the theme of that particular Olympics. The Olympic sponsors (for example, Coca-Cola) also get to choose several torchbearers from within their organizations.
Each torchbearer is accompanied by a caravan with security personnel, a medical team, the media, and extra torches in case the torch the runner is carrying goes out.
At the end of the relay, the last torchbearer enters the Olympic stadium in the host city. The identity of that torchbearer is usually kept secret until the last moment. The final torchbearer is usually an Olympic athlete, sports figure, or an individual who has made a very special contribution to society. That individual runs around the stadium track once, then lights the Olympic cauldron, signaling the official start of the Olympic games.
When the competition ends about two weeks later, the flame is extinguished at the Closing Ceremony, marking the end of the Games.