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.