The Congress shall have Power…To promote the Progress of Science and useful Arts, by securing for limited Tımes to Authors and Inventors the exclusive Right to their respective Writings and Discoveries.
You can read the full text of the Copyright Law of the United States here.
The Copyright Act provides protection and exclusive rights to creators for their works:
Copyright protection begins the moment any “original work of authorship is fixed in a tangible medium of expression.” While a copyright notice or registration enhances protection of the owner's rights, it is not required by the U.S. Copyright Office. In order to claim damages in the event of infringement, creators need to register their publication/creation within 90 days. A copy of the work and a small fee must be deposited with the Copyright Office.
Claims for copyright infringement arise when one or more of the exclusive rights belonging to the author or creator occur, but there are exceptions set out in the Copyright Act. Some of these exceptions are: Fair Use (§107 of the Copyright Act), preservation by libraries and archives (§ 108 of the Copyright Act), and performance and display of works in an educational setting (§110 of the Copyright Act).
Peruse the other sections of this Guide to learn more about Copyright Law, exceptions to the law, and other related information.
There are four factors to consider when determining if something is "fair use" as stated in section 107 of the United States Copyright Act.
Public Domain works are not protected by copyright law and, therefore, they are freely available for everyone to use. There are several ways in which a work passes into the public domain:
Anything in the Public Domain can be used to support instruction, research, publication, and creative work without needing permission from the original copyright owner.