The Elder Scrolls Online will have one big server called a "Mega-Server"

The Elder Scrolls Online features a server technology called "Mega-Server"

Instead of all players being separated on different servers/shards, in The Elder Scrolls Online will have a Megaserver where all players are on one server. The game is smart and knows where to put you, with your facebook friends, guildmates, etc. so that you are always connected.