When I say PVC, people invariably think "pipes", but PVC is used in most plastic products. Office supplies, rain-coats, vinyl siding and flooring, toys, and many other things contain PVC too. It can be either flexible or rigid, it is easily worked with, and is eco-friendly. It is used in many clothes and plumbing systems because it is water-proof.
It is also readily available, because it is made out of oil and salt. It melts at around the boiling point of water, molding easily despite the strength of the plastic.
Now for the molecule itself. PVC is made of massive molecules called polymers. Each one is made of groups of Carbon, Hydrogen, and Chlorine, bound together with covalent bonds. Each bond is single- except on the ends- lending to its lower melting point. The nature of the bonds is very stable and thus leading to a very tough material.