From what i can remember it was an "upgraded PS2" with a DVD recorder and it could view pictures and stuff
http://www.sony.net/SonyInfo/IR/fina...4n-att/psx.pdf
I just found this page of google it pretty much explains it
Also the many people called the PSone PSX so its pretty tricky. If someone is talking about a PSX game though they probably mean a PSone game.