Most of the people get the wrong idea of linux as I used to be. Linux is just the linux kernel. For Windows guys, it is like just like DOS, it is just a terminal, a console. On top of the linux kernel, there is X Windows System. Then on top of it is windows desktop, Gnome and KDE are the famous windows manager we nowadays heard using on most of the distro.

For a novice user, you would not like to want mess around the kernel stuff, you just want the beautiful interface. So, many linux distros come out to save your painful experience on installing linux yourself.

According to DistroWatch, there are more than 369 distro actively maintained by the community. The top 10 major distributions:

1. Ubuntu
2. openSUSE
3. Fedora
4. Debian GNU/Linux
5. Mandriva Linux
6. PCLinuxOS
7. MEPIS Linux
8. Knoppix
9. Slackware Linux
10. Gentoo Linux

One thing I think about Linux community is they should be more united to fight against Microsoft. Rather than starting too many distributions branch that weaken the strength of linux. The linux distro timeline graphics might give you clearer idea how complicated the branch is.