My b2evolution Version: Not Entered

Hi,
I have just used the fantastico option on my control panel to install b2. As usual, with any new digital toy I am very excited. I have spent hours reading posts and the instruction manuals that come with this that are full of great details but I need help to see the big picture.

My first question - why does b2 set up blog "A" and blog "B" with a new user? I have read that it is better to not delete the setup ups but recycle them but I am at a loss of what blog B is for. It seems that blog "B" is still the same user as blog "A".