“Copyright is a form of protection provided by the laws of the United States (title 17, U.S. Code) to the authors of ‘original works of authorship,’ including literary, dramatic, musical, artistic, and certain other intellectual works. This protection is available to both published and unpublished works.”
From the U.S. Copyright Office Circular 1: Copyright Basics [PDF]
Copyright law gives an author of a work a bundle of exclusive rights to do and to authorize others to do the following with the work:
Copyright takes effect the moment a work is fixed in any tangible medium.
It is not necessary to register a work with the U.S. Copyright Office for a work to be protected under copyright law. However, registration does afford certain advantages if the copyright of a work is challenged in court.
Length of copyright term for a work varies and is contingent upon when the work was created, and where it was published. Currently, the basic term of protection is life of the author plus 70 years. If a work is no longer protected by copyright, it is considered to be in the public domain. All works published in the United States before 1923 are in the public domain.
There are a number of exceptions to copyright. The most frequently applied exception for teaching and scholarly use is covered in Section 107, Fair Use.
Section 107 contains a non-exclusive list of purposes for which the use of a copyrighted work would be considered “fair,” such as criticism, comment, news reporting, teaching, scholarship or research. Determining whether a proposed use is fair is case specific, and requires consideration of these four factors:
For more information, see the U.S. Copyright Office Circular 21: Reproduction of Copyrighted Works by Educators and Librarians [PDF]
Creative Commons (CC) is a nonprofit corporation whose goal is to help overcome legal obstacles to the sharing of knowledge and creativity consistent with the rules of copyright. CC provides free licenses and other legal tools to mark scholarly (and other) works so they can be easily shared or remixed within the constraints set by the creator.
CC licenses are not an alternative to copyright. They work alongside copyright to balance the creator's needs with their desire to share their work.
There are six different CC licenses that can be applied to a work. A common example in academia is the Attribution-Non Commercial License (CC BY-NC). This license lets others remix, tweak, and build upon the licensed work; although any new works must acknowledge the original creator(s) and must be non-commercial, they don't have to license their derivative works on the same terms. The logo below accompanies the license and provides a link to its terms: