Most of the Olympics ceremonies are to

The Olympic Games have always included a number of ceremonies, many of which emphasize the themes of international friendship and peaceful cooperation. The opening ceremony has always included the parade of nations.
The Greek team always enters first, and the host team enters last. The torch relay, in which the Olympic Flame symbolizes the transmission of Olympic ideals from ancient Greece to the modem world, was introduced as part of the opening ceremony at the 1936 Summer Games in Berlin.
     Two other important ceremonial innovations had appeared earlier at the 1920 Games in Antwerp, Belgium. The Olympic Flag was flown for the first time. Another was the first reciting of the Olympic Oath, taken in the name of all the athletes by a member of the host’s team. The oath asserts the athletes’ commitment to the ideals of sportsmanship in competition.
     Originally there was another parade of nations during the closing ceremonies of the Games. At the end of the 1956 Summer Games in Melbourne  Australia  however the athletes broke ranks and mingled together to celebrate the occasion. This custom was continued in subsequent Games. After the athletes join in the main Olympic stadium in celebration, the president of the IOC invites the athletes and spectators to meet again at the site of the next Games. The IOC president then declares the Games ended, and the Olympic Flame is extinguished.