A more thorough explanation:

Copyright registration is the process of officially filing a copyright for a creative work with the U.S. Copyright Office. This process is required by law and provides legal protection for the creator of the work.

When someone creates a work, such as a book, song, or photograph, they automatically have copyright protection over that work. However, in order to enforce their rights and take legal action against someone who infringes on their copyright, they must first register their work with the Copyright Office.

To register a copyright, the creator must submit an application, pay a fee, and provide a copy of the work. This process is separate from the requirement to deposit a copy of the work with the Library of Congress.

For example, if a musician writes a new song, they automatically have copyright protection over that song. However, if someone else uses their song without permission, the musician cannot take legal action unless they have registered their copyright with the Copyright Office.

In the 2019 case of Fourth Estate Public Benefit Corporation v. Wall-Street.com, LLC, the Supreme Court clarified that registration must be completed before a person can bring a civil action for copyright infringement. This means that the creator must wait until the Copyright Office has officially registered their copyright before taking legal action.