A warranty is a promise or guarantee given. A warranty is usually a written guarantee for a product, and it holds the maker of the product responsible to repair or replace a defective product or its parts.

A guarantee is an agreement assuming responsibility to perform, execute, or complete something and offering security for that agreement.  It is a promise or an assurance, especially one given in writing, that attests to the quality or durability of a product or service, or a pledge that something will be performed in a specified manner.