This has been asked before too.
Mainly,
Ubuntu is GNOME
Kubuntu is KDE
Xubuntu is XFCE
Edubuntu is different from the former three. It is meant as a teaching aid for students.
Ubuntu has a more polished GNOME interface, KDE of Kubuntu isn't really that well polised as in few other distros. I find XFCe by ubuntu as quite good too.
Well there are a lot of differences between GNOME and KDE. It would be the best for you to google up on these and read up. A good place to start will be their home page and wikipedia.