The preamble for U.S. copyright law states the goal of copyright to "promote the Progress of Science and useful Arts, by securing for limited Times to Authors and Inventors the exclusive Right to their respective Writings and Discoveries." U.S. Const., art. I, § 8, cl. 8.
With some exceptions, copyright protection applies to "original works of authorship fixed in any tangible medium of expression" (17 U.S. Code §102a). Note the words "original" and "fixed" - it needs to be both things. For example, if you have an original idea for a poem but have not expressed it in a tangible medium, that poem is not protected by copyright.
Section 106 of the 1976 Copyright Act gives the owner of the copyright the exclusive right to do and authorize others to
reproduce the work in copies or phonorecords
prepare derivative works based upon the work
distribute copies or phonorecords of the work to the public by sale or other transfer of ownership, or by rental, lease, or lending
perform the work publicly, in the case of literary, musical, dramatic, and choreographic works, pantomimes, and motion pictures and other audiovisual works
display the work publicly, in the case of literary, musical, dramatic, and choreographic works, pantomimes, and pictorial, graphic, or sculptural works, including the individual images of a motion picture or other audiovisual work
perform the work publicly (in the case of sound recordings*) by means of a digital audio transmission
Works federal government employees produced within the scope of their employment
Works clearly and explicitly donated to the public domain
Works that have not been fixed in a tangible form of expression (for example, choreographic works that have not been notated or recorded, or spontaneous speeches or performances that have not been written or recorded)
Titles, names, short phrases, and slogans; familiar symbols or designs; mere variations of typographic ornamentation, lettering, or coloring; mere listings of ingredients or contents
Ideas, procedures, methods, systems, processes, concepts, principles, discoveries, or devices, as distinguished from a description, explanation, or illustration
Works consisting entirely of information that is common property and contains no original authorship (for example, standard calendars, height and weight charts, tape measures and rulers, and lists or tables taken from public documents or other common sources)
This work, "Copyright at The Chicago School of Professional Psychology", is a derivative of "Copyright at the University of San Francisco" by Charlotte Roh licensed under CC-BY. "Copyright at The Chicago School of Professional Psychology", is licensed under CC-BY, by David Sibley