Obtaining a patent is about much more than inventing something new. It is important that you prove it is new. That means you have to compare it to everything that is known in the world already.
The term is "prior art," and it describes the body of everything that is known in the area. It can be daunting, but there are ways to limit your search to prove your idea is new.
All that is known
Before you can claim that your invention has never been thought of before, you have to know everything that ever has been created or written which relates to it. If that sounds impossible, it frankly is. Prior art is a term which describes the theoretical knowledge of everything in the world with the understanding that there are limits to what anyone can discover and describe.
The process of due diligence for filing a patent is a systematic search of literature related to the invention and the components of it. This might include materials, devices, or ways of operating. That is the essence of prior art.
It always starts with a search of patents for examples which are known. If your invention is indeed new, the best place to prove it is not is within the body of patents which have been filed. A thorough search for anything which is remotely the same is the best place to start.
In the body of your patent, it is important to list all prior art that you are aware of and how your invention is different. The reason for this is that this is precisely what the patent examiner is looking for and the easier you can make their job the better.
Your invention will be compared to this prior art to show that it is an advancement over it in some way. The more thoroughly you can describe exactly what the prior art is and why your invention is novel, the better. That is why a deep understanding of prior art is an important place to start with a patent application.
You cannot patent anything which has ever been described in detail anywhere, so your search for prior art has to go beyond patents. All journals, newspapers, or anything else in the field need to be searched for anything which is remotely similar so that you can describe in the patent application exactly why your invention is different.
This can go on forever, since you can never fully prove a negative. But a complete search of everything which is relevant will probably be enough to make your case.
A complex process
Prior art is a simple concept in many ways but in practical terms very complex. It involves a tremendous amount of work and a commitment to a deep understanding of the field.
It's one of the ways in which a patent attorney can be very helpful if you have an invention which you think might be patentable.