Definition - What does Prior Art mean?
The term "prior art" is used in intellectual property law to describe evidence that someone else has already come up with the same or a similar idea for the item that you want to claim as your own invention. This includes any proof that your idea is not new or unique such as drawings, photographs or written descriptions.
Justipedia explains Prior Art
There are few restrictions on what can be classified as prior art. The most significant constraint is that it must have been publicly noted before a new inventor tries to claim the idea.
Today, prior art can be identified by searching various Internet databases containing millions of documents.
The concept of prior art is important because it keeps a new inventor from taking ownership of the idea. Specifically, a U.S. patent cannot be obtained if prior art demonstrates that the idea for the invention has been claimed or publicly noted here or in another country within a certain period.