>>6
To open files, draw on the screen, read from the keyboard, etc., programs call operating system functions. Linux has a different core and provides different functions to do stuff, so you can't run Windows programs on it. (You may actually run a few with a system called Wine, which will emulate Windows functions with varying success.)
>>8
Lol Lunix fanboi
1. Not true
2. If it's so bad, then why did KDE rip it off?
3. You an "use a distro", but unless all you want to do with your computer is write letters to your aunt, browse the intarweb, zoom fractals, and play SuperTux, you really need to install software on it, and this is where Linux totally, intrinsically sucks.