I am not versed at all on turbos. I know how to install...but that is about it.
I know the very basics.
PSI = amount of boost (pounds per square inch)
Boost = Air charge given by supercharger or turbo
I don't know what turbos are good for what motors. Obviously bigger turbo for larger motors.
Check this out for much more info.
http://auto.howstuffworks.com/turbo.htm
http://auto.howstuffworks.com/question122.htm