Azeroth  

Azeroth refers to the original world that Warcraft takes place in. It was understood that Orcs were from another world called Draenor, but the known world and the areas that were fought over were in Azeroth.

What makes this confusing is that the southern end of the eastern continent where the original Warcraft took place is the Kingdom of Azeroth. Even worse, the continent that this kingdom, the dwarven lands of Khaz Modan, and the northern kingdom of Lordaeron are located was also originally called Azeroth before Blizzard decided to rename it to the Eastern Kingdoms.

Azeroth, the world, consists of three main continents, Kalimdor, the Eastern Kingdoms, and Northrend. There is a vast sea between Kalimdor and the Eastern Kingdoms, with a never-ending storm known as the Maelstrom in the center. There are also several island regions such as the human kingdom of Kul Tiras, the Goblin homeland of Undermine, and the islands east of Kalimdor where the Draenei crashed their ship, The Exodar. The Night Elves also created their new world tree off the northwest shore of Kalimdor and named it Teldrassil.

Kalimdor

Prior to a cataclysmic event known as The Sundering, the continents of Kalimdor and the Eastern Kingdoms were one massive super-continent. The massive explosion that nearly destroyed the world annihilated the center of the continent and is where The Maelstrom now exists.

Present-day Kalimdor is home to the Night Elves, and the Horde races of the Tauren, Thrall's orcs, and the Darkspear Troll clan. Since the opening of The Dark Portal, the Draenei have also lived on a cluster of islands in the northwest near the Night Elves. Still, Kalimdor is traditionally considered the Horde's continent, and other Alliance races seldom travel to it before about level 30.

Eastern Kingdoms

The Eastern Kingdoms are the home of the Human, Dwarf, Gnome and High Elf peoples. Through many years of conflict, these peoples have traditionally banded together to form the Alliance. During the third war, most of the High Elves chose to abandon the Alliance and find their own path. Renaming themselves Blood Elves, they eventually joined with the Forsaken with whom they share the northern end of the Eastern Kingdoms. The southern two-thirds of the continent, up to at least the Thandol Span in the Wetlands, are Alliance territory.

Northrend

Much less is known about the frozen continent of Northrend. While it does have its share of lore and stories, most of what is known about Northrend relates to Arthas' trip there to vanquish Mal'ganis, and his battle much later with Illidan at The Frozen Throne.

Northrend will be the setting for the second expansion to the game, Wrath of the Lich King.

The Seas

There are a few points of interest in the great sea between Kalimdor and the Eastern Kingdoms. Small naval kingdoms like Kul Tiras and the goblin home of The Undermine are in far-flung reaches of the world, and the naga led by Queen Azshara lurk in the water below, but the most significant characteristic of the seas is the large, swirling eternal storm known as The Maelstrom.

World of Warcraft Wikibase™

Wrath of the Lich King required!