Difference between 'Turbos psi' and 'Superchargers lbs of boost'

I see lots of people on other sites running turbochargers and they say they run 20psi. Whats the difference between a turbochargers psi and a superchargers lbs of boost?

Is there a conversion? Ie. 10psi = 5 lbs of boost


Thanks for any help.

psi is pounds per square inch. lbs. is the abbreviation for pounds.

Thanks DennyW