A patent is a legal document which provides protection to the ideas of any individual. Usually issued by the Patent Office of a country, the patent is granted to any firm or individual. Usually, patents constitute of four different classes: Machine (a device or apparatus created by a person for the performance of a specific task, process (a process created by an individual), manufacture (any fabricated or manufactured product) or the composition of matter (any chemical mixture or compound created by a person). Patents can be sued for.