Azeroth

Prehistory

 Azeroth is the world where the Warcraft series takes place. In the past, Azeroth was ruled by the Old Gods and their Elemental Lieutenants. The world was at peace until the Titans arrived and attacked the Gods. The Titans managed to kill one God and imprison the rest. After that battle, the rest of the Gods abandoned Azeroth, leaving only the Great Aspect to watch over the world.

The split of the Kalimdor

 Years later, the trolls were born. As their empire grew, so did the Azj'Aqir Empire. The trolls were losing until the Aqir split into the  Qiraji and the Nerubians. The Night elves then appeared and built a magical empire around the Well of Eternity. Later, the Burning Legion invaded Azeroth in the War of the Ancients, during which the Well of Eternity was destroyed. This act split the world into several continents.

Continent of Azeroth

In the Eastern Kingdoms, the southernmost part is known as the Continent of Azeroth and is where the Human capital city Stormwind is located. This is not to be confused with the world Azeroth. 
 

The Cataclysm 

 Deathwing's escape from his underground prison overhauled the world of Azeroth in an event known as the Sundering.  Areas of Azeroth now find themselves completely changed.   Thousand Needles is completely under water.  A maelstrom has separated Stranglethorn Vale into two separate areas.  The island and underwater lands of Vashj'ir have become known to the land-dwelling races of Azeroth. 
 
Northrend escaped the Sundering untouched, but the mark of the Sundering can be found on nearly every other area of Azeroth.