Patents generally govern inventions. The patent system was designed to encourage inventors to share their creations with the community. These creations can be almost any sort of machine, process or, in some cases, a design. It does so by providing a limited amount of time for which the inventor (or their assignee) has the right to prevent others from making, selling or using their patented item. The length of that grant of exclusivity through a patent varies by country. In the US it is “… for a term beginning on the date on which the patent issues and ending 20 years from the filing of the application.” (35 USC sect. 154)
The patent process in the US is governed by the US Patent and Trademark Office, generally referred to as the USPTO. This is where you begin the process of applying for a patent. The process is known as “Patent Prosecution” and is done with the assistance of an attorney admitted to the Patent Bar. These attorneys generally have a background in science or engineering and have extensive training in patent law.
But getting a patent is just the start. Now you must protect your patent rights. The biggest problem is infringement, that is, someone using your patent to manufacture your device or use your patent in their own invention and patent process without your permission.
There can also be challenges to the validity of your patent. Another party may claim that your patent is invalid or should never have been granted. One of the reasons a patent may be challenged is that the subject of the patent is not new or that it would be so obvious to an expert in the field that it fails on the basis of originality. Another attacks the patent as involving subject matter is not patentable matter at all.
In the US these challenges take place in civil court and you would be represented by a litigation attorney. Generally, the patent holder seeks two things: an injuction against the infringer which would prohibit him from continuing the infringing behavior and monetary compensation based on the damaging monetary impact of the infringement. The latter can be demonstrated by evidence of a loss of income due to the infringement, which can include things like lost sales or loss of income from licensing.
Patents are granted to the inventor/inventors of the subject of the patent. The ownership of the patent can be assigned to another party or use of it can be licensed to another party. To arrange for licensing or assignment you should consult attorney with experience in such matters.