raspberry pi gushing

in class today i saw a raspberry pi. i realized ive never actually seen one. there was two. one was this big spider thing and its display was connected to a tv, and the other was just the board and a teeny tiny lcd. the spiders wallpaper was amazing, and the tiny one had chromium and dolphin and a terminal open. i want to know more about them,, the desktop looked like the older versions of KDE... i want to see what they run on really bad... i hope its debian... or ubuntu... i wonder if you can install those... i should get an rpi... or a vm of whatever os they run... theyre so cute...