http://eu.battle.net/Battle.net Account
Beginning with World of Warcraft®, the new Battle.net account grants access to Blizzard Entertainment games, websites, and online services - all with a single e-mail address and password.
https://eu.battle.net/faq/index.htmlQ: What is a Battle.net Account?
A: As part of our ongoing improvements to Battle.net, we are introducing a centralized account system that will let players manage all of their Blizzard Entertainment games, including World of Warcraft and future games, in one place without having to remember multiple sets of login information.
Q: Are these Battle.net Accounts related to Blizzard Accounts?
A: Battle.net Accounts are an evolution of the existing Blizzard Accounts. If you already use a Blizzard Account, you do not need to create a new Battle.net Account -- the Blizzard Account has been automatically converted, and people with existing Blizzard Accounts have received an email containing more information.
Blizzard/Battle.net Mobile Authenticator