What do the Olympic rings represent?

As it says in the Olympic Charter, the five-ringed symbol "represents the union of the five continents and the meeting of athletes from throughout the world at the Olympic Games." Baron Pierre de Coubertin, the founder of the modern Olympic Movement, conceived both the symbol and the flag.

Symbolism of the Olympic Rings:

The five interlocking rings represent the five continents brought together by the Olympic Movement, or the five main regions: Africa, the Americas (North and South America are combined), Asia, Europe and Oceania. The symbol of the Olympic Games is composed of five interlocking rings, colored blue, yellow, black, green, and red on a white field. The colors of the rings represent the flags of the countries that participate in the Olympics. Every flag of a country participating in the Olympics includes one of those colors.

The Meaning of the Colors on the Olympic Flag.

The following is quoted directly from the International Olympic Committee: "The five rings represent the five continents. They are interlaced to show the universality of Olympism and the meeting of the athletes of the whole world during the Olympic Games. On the Olympic flag, the rings appear on a white background. This flag translates the idea of the universality of the Olympic Movement. At least one of the colors of the rings, including the white background, can be found on the flag of every nation in the world."

The way in which the rings are interlaced has changed since the symbol was first introduced. They used to be depicted side-by-side, along a shallow arc. They are now drawn in the familiar offset pattern, with three above and two below. They are colored, from left to right: blue (top), yellow (bottom), black (top), green (bottom), and red (top). The five rings represent the five continents of Earth.
The Five Rings on the Olympic Flag The rings on the Olympic flag represent the five continents of the world that have come together in the Olympic spirit. Every country in the world has at least one of the colors of the rings in their flag, blue, black and red (top colors) ´Żą yellow, green (bottom colors).
They represent the five parts of the world (commonly referred to as continents): Asia, Americas, Africa, Europe, Oceania. Both the Americas were taken as one, Antarctica was not counted.