WHAT IS A PATENT?
A patent is the exclusive right to prevent others from making, using or selling the invention or things made using the invention. A patent does not give you the right to make, use or sell the products of your invention since your patent may have aspects which were previously patented by another person or entity.
The easiest way to understand this is to consider a patent on the combination of elements "A, B and C." It may be patentable. However, if another person has already patented the combination "A and B", you cannot make the combination "A, B and C" without infringing the patent for the combination "A and B." In patent terminology, your patent is dominated by the "A and B" patent. In many cases, it is possible to license the combination "A and B" from the patent owner. Alternatively, the patent owner of combination "A and B" may be a highly likely purchaser of a license or assignment of your patent on combination "A, B and C." Once you have filed your patent application and prosecuted it to issue, the owner of the "A and B" patent cannot make the "A, B and C" combination without securing from you the right to do so. "A, B and C" is your patented invention and you have the right to enforce it in court.
A patent has long been thought of as a monopoly granted by a sovereign government for a period of time (in the United States, twenty years from the date the application for patent is filed). In exchange for this monopoly, the sovereign requires the patent owner to fully disclose the invention so that others are enabled to make and use the the patented invention after the patent expires. At the end of the patent term, the patented invention or discovery becomes dedicated to the public.
As stated above, the rights in a patent can be sold. This is done via a license or an assignment. Like other forms of property such as real property (land and buildings) and personal property (gold, cars and antiques), intellectual property may bought and sold. The transfer of the entire bundle of rights created by a patent is termed an "assignment". An assignment is in writing and must be recorded in the United States Patent and Trademark Office (USPTO). Alternatively, the intellectual property owner has the option to choose to convey only a portion of his or her ownership rights. Conveyance of limited rights in intellectual property is termed a "license."
The primary requirements for a patent are that the invention or discovery must be novel, useful, and non-obvious to a person skilled in the technology or art to which it pertains. A patentable invention is most often the result of extensive trial and error directed to overcoming a specific problem. It may also happen in a moment of keen insight. Either way, for the solution to become patentable two things must occur. First, the inventor or discoverer conceives of a solution to overcome a problem. Second, the solution must be reduced to practice. The second requirement may be met by an actual reduction to practice. Alternatively, it may be met by constructively reducing the invention to practice by the filing of a patent application.