Ok I am really clueless on something.

The whole concept of scripts on sites...

I can design a site, I can make nice graphics but I don't understand what exactly is a "script" and how it works in a site such as - kawaiispace.com

Like if someone says MY SCRIPT ON KAWAIISPACE IS ON SALE - what does he mean?

And is it easy to install a script? It's better to know the script than design after, so once can base the design around the script no?

Somoene help me out on this please, I'm really confused for this thing.