There are two longstanding legal devices for defining and protecting different sorts of intellectual property: copyright, and patent. Copyright was originally introduced to define ownership in “literary works”, such as novels, poems, or non-fiction books, but came to be extended by analogy to things like musical compositions, films, and so forth. Patents relate to newly-invented machines or industrial processes.
Neither copyright nor patent law was part of the Common Law; both devices were introduced by statute. (Indeed, the USA has had a general law of copyright only since the 1890s - it was a standing grievance for Victorian novelists that no sooner did the fruits of their labour emerge from the press than American publishers’ agents would rush single copies across the Atlantic, where they would be reprinted and sold without reward to the author.) The original motivation of both copyright and patent law was the same: they were intended to stimulate advances (in literature, and in industry) which would benefit society, by creating concrete incentives for the innovators.
The kinds of protection offered by the two areas of law are different. Copyright is something that the author of a “literary work” acquires automatically in producing the work, and it forbids anyone else to make a copy of the work (for a set number of years into the future, and with various provisos that do not matter here) without the right-holder’s permission. Thus an author’s copyright is a piece of property which he can sell or license for money; in the case of books, typically a publishing company contracts with an author for permission to publish his book in exchange for royalties paid to him on copies sold. With newer media such as films, the business models are different, but the underlying law (which is what concerns us) is essentially the same.
A patent, on the other hand, is not acquired automatically by the inventor (or anyone else). Taking out a patent is a complicated and expensive undertaking, but if a patent is granted, it forbids anyone (again, for a set future period) from exploiting the process or mechanism without the patent-holder’s permission; so again the patent is an economically-valuable piece of property, which can be sold or licensed to companies wanting to use the innovation in their business.