nak-1 is correct, the difference is in how you install. For example Mandrake, Fedora Core, Suse are newbie distros and very easy to install. Debian, Gentoo, Slackware and etc are expert distros and harder to install. Also the difference is in speed and stability, the expert distros tend to be a lot more stable. Then there are live cd distros such as Knoppix which you do not need to install, and run from the cd.