Basically, it's a free (for one year) version of Visual Studio, which is slightly cut-down and only supports Visual Basic. There are also several other Visual Studio Express products including Visual C#, J# and C++.
The Registration Benefits page also is very interesting.
We are offering thousands of dollars worth of resources from Microsoft and third-party partners to ensure that you have a great experience with the Express Editions.Basically these resources include eBooks and royalty-free graphics including icons for use in your super-leet 'Hello Worldz0r' Visual Basic 'app'.
Hey, but in all seriousness, this seems pretty cool, at least for people just getting into programming and interested in Visual Basic (although whether or not that is a good place to start is debatable). And it will probably decrease the amount on piracy of Visual Studio.