A warranty on a product or service is a guarantee of replacement, repair, or refund in the case of damage or dissatisfaction. A limited warranty is any warranty that is not complete or has various restrictions placed upon it. Truly unlimited warranties are extremely rare as most products do tend to wear out after a long enough time. An unlimited warranty would actually only be limited by the life of the company that offered the warranty in the first place; that company would probably end up losing money if it replaced each and every product that ceased to work properly. Limited versions, then, are far more popular, though the precise limitations placed on a warranty can differ significantly.
The cost of a limited warranty is often included in the price of a product. Many companies promise to replace products if they are damaged or unusable when purchased. This warranty, however, usually only lasts for a short period of time depending on the product. For many more expensive products, one can pay extra to extend the warranty. Many computers, for example, come with a one-year limited warranty that can be extended for another year or two if one pays for the extended warranty.