What do the Olympic rings signify?

According to most accounts, the rings were adopted by Baron Pierre de Coubertin (founder of the modern Olympic Movement) in 1913 after he saw a similar design on an artifact from ancient Greece.  The five rings represent the five major regions of the world: Africa, the Americas, Asia, Europe, and Oceania. Every national flag in the world includes at least one of the five colors, which are (from left to right) blue, yellow, black, green, and red.  It is important to emphasize that Pierre de Coubertin never said nor wrote that the colors of the rings were linked with the different continents

The Olympic Flag made its debut at the 1920 Olympic Games in Antwerp, Belgium. At the end of each Olympic Games, the mayor of that host-city presents the flag to the mayor of the next host-city. It then rests at the town hall of the next host-city for four years until the Opening Ceremony of their Olympic Games.