What is a limited slip posi?

i have a 91 caprice and i noticed that if i try to do a burnout my tires dont spin the rear just raises and revs. I entered my vin number into Compnine.com and it said AXLE,REAR,POSITRACTION,LIMITED SLIP POSITRACTION L/SLIP R/AXL(G80).. Does this mean my car has a posi or no?