"Developed by the team at Zenimax Online Studios, The Elder Scrolls Online merges the unmatched exploration of rich worlds that the franchise is known for with the scale and social aspects of a massively multiplayer online role-playing game. Players will discover an entirely new chapter of Elder Scrolls history in this ambitious world, set a millennium before the events of Skyrim as the daedric prince Molag Bal tries to pull all of Tamriel into his demonic realm." -GameInformer
A recent Elder Scrolls Online article gives us information about when the beta will start, how it will play out, and other additional information.
A closed beta is beginning soon, and everyone has an opportunity to sign-up.