We discuss the need to do a patent search to find prior art.  What is prior art that the patent search is supposed to find?

Prior art does not need to exist physically or be commercially available. It is enough that someone, somewhere, sometime previously has described or shown or made something that contains a use of technology that is very similar to your invention.

A prehistoric cave painting can be prior art. A piece of technology that is centuries old can be prior art. A previously described idea that cannot possibly work can be prior art. Anything can be prior art.

An existing product is the most obvious form of prior art. This can lead many inventors to make a common mistake: just because they cannot find a product containing their invention for sale in any shops, they assume that their invention must be novel.

The reality is very different. Many inventions never become products, yet there may be evidence of them somewhere. That evidence – whatever form it may take – will be prior art.

Prior Art under 35 U.S.C. §102(a)
A patent or literature reference by another that is published (printed publication) or laid-open before the invention thereof by the applicant for patent (generally, prior to an applicant’s U.S. filing date) is available as prior art under 35 U.S.C. §102(a).
The term “by another” includes any difference in inventive entity, even among multiple inventors. For example, if X and Y file a patent application, and if X and C disclose the invention in a literature reference that is published prior to X and Y’s U.S. filing date, than the subject literature reference is available as prior art under 35 U.S.C. §102(a).
Prior Art under 35 U.S.C. §102(b)
A patent or literature reference by anyone that is published more than one year prior to an applicant’s U.S. filing date
is available as prior art under 35 U.S.C. §102(b).
An inventor’s own publication can not be applied as prior art under 35 U.S.C. §102(a), so long as a U.S. application is filed within one year of the publication date. This is called the “grace period” and is unique to United States patent law. For example, in many countries, the inventor’s public disclosure prior to filing a patent application defeats novelty. However, if published more than one year prior to applicant’s U.S. filing date, even the inventor’s own publication can be applied as prior art under 35 U.S.C. §102(b).
The provision of §102(b) is called a “statutory bar”. That is, a §102(b) reference cannot be removed or antedated under any circumstances. When the examiner cites a §102(b) reference and assuming that the rejection is well founded, the applicant must then amend the claims to distinguish over the prior art.
Prior Art under 35 U.S.C. §102(e)
The provisions of §102(e) relate to U.S. patents, published U.S. patent applications and PCT applications published by WIPO. A U.S. patent or published U.S. patent application, by another, is available as prior art as of its effective U.S. filing date. A PCT application, by another, designating the U.S. and published by WIPO in English is available as prior art as of its PCT filing date.
The importance of a trademark search is to find prior art to make sure that an invention is able to be protected by a patent, and to make sure that there are as few roadblocks on the way to get the registration as possible.