normal/utility category

I know it's back to basics, but I still don't quite have this one down.
A Mustang II is rated at 1600 lbs in the utility category, but no spec
is given for the normal category. Normal cat will allow a higher weight
capability, AIUI. Is the difference between the two based solely on how
hard you G-load the plane during flight? What about landing weights or
if you prang it pretty hard? (Of course, none of US ever do that!) 8-).

Thanks.