True south is the direction towards the southern end of the axis about which the earth rotates, called the South Pole. The South Pole is located in Antarctica. Magnetic south is the direction towards the south magnetic pole, some distance away from the south geographic pole.
It is the direction to the right of an observer facing east.
The term The South is often used to refer to the less culturally and technologically advanced nations of the world (or, more generally, to regions within particular nations).