A patent is a grant from a patent office, such as the United
States Patent Office. "Patent Pending" is a phrase that an
application for a patent has been filed and is in some stage in the
process of obtaining a patent. Thus, a patent can be presently
enforced while a patent that is merely pending is unenforceable but
can mature into a patent that can be enforced. Once the pending
patent matures, the patent owner can sue for back damages or
reasonable royalties starting from the filing date of the
patent.