Copyright law (defined here) protects "original works of authorship fixed in any tangible medium of expression" for a time period. As an example, copyright protects the legal right to publish and sell musical, literary, or artistic works--and protects producers, publishers, authors, and the public. It works for both traditional media and digital media like e-journals and websites. Works protected by copyright include:
Ownership of copyrighted work means that you have the right to control the use of that work, so use of the work by others either requires permission from the author, or copyright holder, or reliance on Fair Use. Failure to procure permission or usage under fair use would expose users to copyright infringement. Learn more at the U.S. Copyright website.