Repositionable adhesive window decals use a special sticky backing, much like other stickers, to affix the product to glass or other smooth surfaces such as walls. Repositionable adhesive can be removed easily and repositioned up to five times before the adhesive starts to break down.
Static window clings don't use adhesive at all, but instead a static-charged back surface that allows them to cling to a glass surface. Static window clings can be removed easily and repositioned again and again, but do not have the same sticking strength as a stock with adhesive and typically only adhere to a glass surface.