Kde is a desktop enviroment for the X11 system, commonly used by Linux with XFree86 and xorg. Commonly used.
Matthias Ettrich started KDE in 1996. It uses the Qt graphic library. Based on "look and feel" and features. KDE is extremely powerful for experts and easy to use for beginners at X.
Has a whole stash of software. Such as KOffice, Kmail, kontact, the K edutainment suite, KDE games, and etc.
File Manager: konqueror
Window Manager: kwin
"no that's just KDE, wait it out man"