What do Spin off Series in Vampire Academy books mean?

it means we are still in the same world with all the moroi, dhampirs, strigoi, blah blah. but the story is not about Rose anymore. they're going to be from 3st person pov. in bloodlines (coming out August 2011) the main character is Sydney. and we see more of Jill (aka Jailbait). hopefully the main male character (who Mead said is going to be a surprise) is Adrian.