In artwork, the subject matter would be what the artist has chosen to paint, draw or sculpt. In patent law, the subject matter would be the technical content of a patent or patent application found in the description, claims and drawings.
In other words, subject matter is what the inventor has choosen to invent, and in a patent application the inventor must reveal the subject matter (invention) in a way dictated by law.
Example 1 The specification must conclude with a claim particularly pointing out and distinctly claiming the subject matter which the applicant regards as his invention or discovery.
Example 2 The distinction between patentable and unpatentable subject matter continues to be a topic of debate among software developers, academics, lawyers, and USPTO examiners.
Example 3 The patented subject matter, and additional subject matter still pending in the US and foreign patent offices, includes claims to methods and devices for delivering medicinal substances to the interior of cells in various body tissues