Open coil springs are connected together, so when you lie on the bed all the springs absorb some of your weight - and they also all move. There is little if any motion separation. Pocket springs are not connected to each other but are held in their own fabric pockets. Only those springs in contact with your body actually move. Pocketed springs are best for couples since when one person moves, the springs move individually and not all at once. They are best for motion isolation. Also, avoid open-coil spring mattresses for orthopedic use since they tend not to use enough foam padding to make them truly comfortable. Luxury or premium hybrid mattresses tend to be constructed using pocketed spring coils.