What is a patent pending?

It means that a patent application for an invention has been filed. Therefore the patent is "pending." A patent based on that application may eventually issue or it may never issue, depending on the examination and prosecution.

"Patent pending" means that the owner of the product has submitted an application to the USPTO but the patent hasn't been granted yet.

Legally - patent pending means that a patent application has been filed in the USPTO on the invention.

The term "Patent Pending" or "Patent Applied For" means that you currently have a Patent Application pending or patent rights protected in the geographical region where the product is being made, used, or sold. If you mark a product "Patent Pending" in the U.S., and there is no Patent Application pending in the U.S. Patent Office, you may have committed a fraud which could jeopardize your Patent if you subsequently file a Patent Application and a Patent is then issued. Patents are territorial by nature. If you want to market the product in Canada, you may eventually need to file a Patent Application in Canada. It is recommended that you consult with a Patent Attorney or Patent Agent if you have an invention that you want to protect.

"Patent pending" means that the producer of the product has filed a patent application that they believe covers the product that is labeled with "patent pending." It does not mean that they have a registered patent, it mostly means that there is a possibility that some day they may have a patent registration and that if you copy the product you are at some risk of future legal issues.

"Patent pending" on article or associated with a method, process or device means that one or more applications under review at a patent granting authority such as the USPTO are considered to be relevant to the article method or device.