warranty (or extended warranty) is broadly defined in law as a contract for cover for goods, which is entered into by a consumer for monetary (money) consideration. A warranty is a form of insurance policy which provides cover for the unexpected failure or breakdown of goods, usually after the manufacturer's or trader's guarantee has run out but it can cover the same time period as a guarantee because it may offer additional cover. Check the start date of the warranty before you go ahead. Some warranties are service contracts rather than insurance backed (you should check the status of the warranty before you purchase it) . Warranties can vary - they offer different protection, from the most basic cover to those which provide comprehensive cover. For instance, you may be covered only for the 'market value' of the goods, which means their second hand value after use or you may be covered 'new for old'. Do not assume that a warranty will provide cover for all problems encountered with the goods. They usually have exclusions that set limits on the cover you receive.
A warranty or extended warranty is additional to the legal rights you have as a consumer and must not affect those rights in any way.