Inventors and the PTO
One of the most basic players in the role of patent law is the inventor. He or she dreams up the idea, known as 'the invention' and creates it or has someone else create it for them. The act of creating an invention is known as reducing it to practice. At this point, the invention has been physically created, its fully operational and complete, and its full utility is known.

Inventors may be employees at a major corporation, employees at a small company, or the lone individual working out of their home or garage. 

Inventors may invent something as simple as the paperclip or as complicated as a rocket propulsion system. Either way, once their invention is complete and in working order, an inventor may apply for a patent to the United States Patent and Trademark Office (USPTO or sometimes just PTO). This sub-branch of the Department of Commerce is located in Alexandria, Virginia.

In addition to the vast library archives of patents, there is also an active component at the PTO. This component includes the departments involved in receiving, processing and examining new patent applications. The individuals responsible for examining the patent application are known as patent examiners.

Examiners
Patent examiners are fairly well paid individuals who scrutinize the patent applications assigned to them, ultimately determining whether or not the application is worthy of a patent. Examiners check the invention in regards to previous inventions and review all sorts of reference materials attempting to determine whether the idea really is new. If the idea isn't new it will not qualify for a patent.

After reviewing an application, the examiner will send a complex bundle of paperwork back to the applicant and expect an appropriate reply in a timely manner. No matter how wonderful the idea is, a patent will not be granted if the application is not satisfactory. For instance, does the invention outlined in the application overlap with anything created in the past? Is it obvious?  Is the invention even patentable at all? Some things like ideas are not patentable.

Patent Practitioners
It is for this reason that many inventors decide to hire an individual skilled in patent law; a registered patent practitioner. There are two types of patent practitioners; patent agents and patent attorneys. Both have the proper skill set, which involves training in science or engineering. Both have passed a qualifying exam known as the Patent Bar exam and both may write and prosecute patents. This means they may aid in the examining process by attending interviews with examiners and writing amendments and appeals. What separates the two is essentially a law degree.

Patent attorneys have completed a law program and may practice in regular courts of law in addition to within the USPTO. A patent attorney may help protect and uphold the rights granted to a patent holder in an infringement case. In addition, patent attorneys usually charge more than agents, although a particular inventor may not ever need these extra services.  Patent agents may not practice in regular courts of law, but they may write and prosecute patents.

The most important aspect from an inventors viewpoint is that the patent practitioner is trained in the field of their invention. For instance, a biotech company desiring to gain a patent on a new drug will need a patent practitioner with a background in biochemistry or molecular biology. An inventor who invents a new type of farm equipment will need a patent practitioner with a background in mechanical engineering. This level of specificity is required because it really is important that the patent practitioner completely understand what's been invented so they can convey that in the application. In addition, they need to be able to review and understand similar already existing inventions to see exactly how they are different from the new invention of their client.