It's an add-on to Visual Studio. It's specifically targeted at database development. It manages all your database objects locally through scripts that can be checked into source control. It has a full unit test engine. It has a build & deployment mechanism that can be automated along with the TFS (Team Foundation Server) build mechanisms. It has exactly one, at this point, refactoring mechanism built in. Here's the web site:

http://msdn.microsoft.com/vstudio/teamsystem/dbpro/

We've been evaluating it. It looks likely that we'll be adopting it and it's associated processes, even though it's in CTP, as our database development tool.