Copyright is actually an "intellectual property." Intellectual property is "An asset with a prime value which derives from the product of human knowledge, discovery, invention or mental creativity. Intellectual property covers a host of different types of product, e.g. a new drug, film or pop song, piece of computer software, book, cooking recipe, photograph, television game show format, the television rights to a football game, an innovative steel manufacturing process" according to Credo Reference, The New Penguin Business Dictionary. So it differs from physical property in that it's not initially tangible. There are several forms of intellectual property protected by law. Usually they are broken into two categories, copyright, the one most people know, and industrial property including: trademarks, patents, and trade secrets. Interestingly, in the United States, the Copyright Office is a division of the Library of Congress while the Patent and Trademark Office is an agency of the Department of Commerce.
For more on intellectual property, see these resources: