Features:

Requires original World of Warcraft game
An increase in the level cap to 70
Two new playable races, including the magical Blood Elves
New starting zones in QuelThalas and beyond
The entire new continent of Outland, reachable through the Dark Portal
Many new high-level dungeons to explore in Azeroth, Outland, and elsewhere
New flying mounts in Outland
Many new and dangerous monsters, including epic world bosses
Hundreds of new quests
Hundreds of new items
A new profession: Jewelcrafting
Socketed items And much, much more...