In the context of patents refers to the disclosure of the invention. Patents are sometimes described as a bargain with the public, under which the inventor discloses his or her invention in return for the time-limited exclusive rights provided under the patent. Disclosures are usually supposed to be in writing and for this reason are sometimes referred to using the term in found in the US patent statute “written description.” See Enablement, Continuation-in-Part.
In principle a patent can only claim what is disclosed in the body of the patent; this is why it is important to make sure that the disclosure in a patent application is sufficient to support a range of possible claims to what the inventor has in fact disclosed. An inadequate disclosure can only be fixed by filling additional disclosures, at the potential cost of a loss of the original priority date, or a mixed priority date as in a continuation-in-part.