Copyright is a form of protection grounded in the U.S. Constitution and granted by law for original works of authorship fixed in a tangible medium of expression. Copyright covers both published and unpublished works. It protects original works of authorship including literary, dramatic, musical, and artistic works, such as poetry, novels, movies, songs, computer software, and architecture. Copyright does not protect facts, ideas, systems, or methods of operation, although it may protect the way these things are expressed.
SOURCE: FAQs: Copyright in General from U.S. Copyright Office. Accessed 4/1/2020.
Copyright issues are important to education and libraries. Consequently, these institutions devote time and resources to understanding the nuances of the laws and explaining it to faculty, students, and library patrons.
"A work of authorship is in the “public domain” if it is no longer under copyright protection or if it failed to meet the requirements for copyright protection. Works in the public domain may be used freely without the permission of the former copyright owner."
SOURCE: "Where is the Public Domain?" in Definitions (FAQ) from U.S. Copyright Office. Accessed 4/1/2020
The U.S. Copyright Office administers the copyright laws of the United States and provides impartial expert advice on the copyright laws. Their website, Copyright.gov, provides a wealth of resources. Here are a few links to help you quickly find information.