As far as I know only those who preorded the game should be able to create any race on any factions, so you probably got a copy of the preorder edition wich is great.
The alliances effect wich starter place you begin with, and wich banner your fighting for in the alliance war (PvP). After you complete the main story and reach level 50, you will be able to travel to the other factions and quest on there alliance as a shadow ish hero. The NPC's will think your one of them etc, but you wont be able to see other factions except your own, and the enemys will be around your level.
Medakon - Legendary Super Hero Professional Assassin Nightblade from Tamriel who do different stuff