Shrink film is a material made up of plastic film. When heat is applied to this material it shrinks tightly over whatever it is covering.
Shrink-wrap is one of the most popular forms of packaging, and usually one of the most inexpensive forms of packaging. Shrink wrap protects the product. Shrink-wrap is used for making multi-packs such as commonly found in Sam's, Costco, and most major retailers.