Factory warranty is basically a contract with the manufacturer. Under this contract, the manufacturer absorbs either the repair or replacements cost for a pre-defined period of time.  It benefits the customer by exempting them from spending over the purchased price during the contract duration.
 
How does one extend the factory warranty?

Different factory warranty plans are available for different models and vehicles. One can choose from different plans according to their needs and demands. If the factory warranty has expired, one can extend the plan further. A plan can be purchased for a long duration and with wholesale pricing.

Benefits:

The basic benefit lies in the cost cutting of the customer. It essentially helps if there are major defects, which were not detected at the time of purchase. However, it will offer you a much more comprehensive coverage if the warranty is obtained from a warranty adviser, instead of a car dealer.