The south pole of a magnet is the one attracted to the south pole of the earth. This south-seeking pole is identified by the letter S. By accepted convention, the lines of flux travel from the north pole to the south pole.
The geographic South Pole is the southern of the two points on the earth's surface through which the earth's rotational axis passes. For an observatory at the South Pole, any given star maintains a constant elevation (distance above the horizon) as the earth rotates. On most maps the South Pole is either left off altogether or stretched out to form the entire bottom edge of the map. On most blow-up plastic globes it is obscured by the manufacturer's logo and a sign that says "Made in China". None of these things applies to the real South Pole. There is also a magnetic South Pole, which is where you end up if you follow your compass, and a geomagnetic South Pole, Neither of these is anywhere near the geographic South Pole, although both are in or near Antarctica.
When not otherwise qualified, the term South Pole normally refers to the Geographic South Pole – the southernmost point on the surface of the Earth, on the opposite side of the Earth from the North Pole. Other "South Poles" described in this article include the Ceremonial South Pole, the South Magnetic and Geomagnetic Poles, and the Southern Pole of Inaccessibility.