A patent is grant of exclusive rights for an invention to make, use and sell the invention for a limited period of 20 years. The patent grant excludes others from making, using, or selling the invention. Patent protection does not start until the actual grant of a patent.
A patent owner has the right to decide who may or may not use the patented invention for the period in which the invention is protected. The patent owner may give permission, or license, to other parties to use the invention on mutually agreed terms. The owner may also sell the right to the invention to someone else, who will then become the new owner of the patent. Once a patent expires, the protection ends and invention enters the public domain, that is, the owner no longer holds exclusive right to the invention which becomes available to commercial exploitation by others.
The patent system is desirable in the public interest that industrial techniques should be improved. The monopoly rights are granted in lieu of disclosure of the invention i.e advancement in technology. In order to encourage improvements and to encourage also the disclosure of improvements in preference to their use in secret. Any person devising any improvement in a manufactured article or in machinery or methods for making it, may upon disclosure of his improvement at the Patent Office demand to be given a monopoly in the use of it for a limited period. After that period, it passes into the public domain.