The para cord is nylon and won't rot or mildew, very strong for its size, it also won't break down if left outside in the sunlight like polypropylene does. Nylon rope or para cord will stretch, and absorb water.
Polypropylene rope will float and stretch, it won't absorb water; and you can melt the cut ends just like nylon to keep it from unraveling.
Hemp or "regular rope" sorry I can't thing of the name right now; will rot, does absorb water; it doesn't stretch as much and the sun doesn't bother it.
Lots of uses, learn your knots and their different uses. Good luck and have fun.