Copyright is a form of protection provided by the laws of the United States (Title 17, U.S. Code) to authors. The copyright owner has the exclusive right to do and authorize the following:
Copyright protection covers both published and unpublished works, as well as out-of-print materials. Copyright protection lasts for the life of the author, plus 70 years.
The public domain refers to works that are not subject to copyright or intellectual property laws. These works are owned by the public, and anyone may use these works without obtaining permission.
Here are four ways a work may arrive into the public domain, from Stanford University's Public Domain guide:
Works prepared by an officer or employee of the U.S. Government, as part of that person's official duties, are in the public domain. However, works created by state or local government employees are likely protected by copyright.
Cornell University maintains an extensive guide to types of works in the public domain. See Copyright Term and Public Domain in the United States.
This guide is meant to provide guidance for resolving basic copyright questions. The content in this guide does not constitute legal advice and is not intended to replace the advice of legal counsel.
Copyright Law of the United States: This publication contains the text of title 17 of the United States Code, including the Copyright Act of 1976 and all subsequent amendments to copyright law.
Digital Millennium Copyright Act (DMCA): Set rules and penalties to protect copyrighted material on the Internet.