The answer is that positive supercoiling involves the formation of new coils in a protein, while supercoiling does not.
Positive supercoiling is when a protein folds up into a shape that takes up less space than its original structure (in other words, it folds into smaller loops and turns itself inside out). This type of folding is reversible, meaning that if you heat the protein back up to room temperature, it will resume its original shape. Supercoiling occurs when there are more coils in one direction than another – for example if your protein has two partially-folded regions (a head and a tail), but that head and tail have different numbers of coils.
Supercoiling can cause problems when proteins fold incorrectly and don’t return to their original shape after being heated up. Because they get stuck in this state, they don’t work properly anymore – they may be unable to fold into their correct 3D structure or they may become rigid because of the extra coils formed on them.