There's a lot of differences (if there wouldn't be, there would be no need for all those distro's now would there?) but i'm not gonna list them, that's what sites like http://distrowatch.com/ , http://www.linuxiso.org/ , http://www.linux.org/dist/index.html and http://www.frozentech.com/content/livecd.php are for, each has lists of distro's and descriptions of their use and content.
