There are only two versions of PSP. Original (some called it
"Fat" 
) and Slim. Slim/lite
probably just mean Slim.
The "version" your friend is referring to would be of PSP's
firmware, which is what enables the console to run ahem games after
modification. I don't have much info on this, but I'm sure if you
ask teh unker who sells the console about getting a modded PSP that
can play ahem games, he won't report you to the police or
something.
