A more thorough explanation:

The United States Copyright Office is responsible for managing and administering copyrights in the United States. It is a department of the Library of Congress.

When someone creates a work that is eligible for copyright protection, they are automatically protected from infringement. However, if they want to take legal action against someone who has infringed on their copyright, they must register their work with the Copyright Office.

For many types of works, individuals must also send two copies of their work to the Copyright Office or face a fine. The Copyright Office maintains a catalog of all registered copyrighted works, which allows individuals, businesses, and the government to search for existing copyrights.

In addition to administering the registration of copyrighted works, the Copyright Office also plays a key role in shaping copyright policy. Congress gives the Copyright Office the authority to create regulations for much of U.S. copyright law, and the executive, legislative, and judicial branches of government often look to the Copyright Office for guidance on copyright issues and changes to copyright law.

For example, if a musician writes a song and wants to make sure no one else can use it without their permission, they can register the song with the Copyright Office. This will give them legal protection and the ability to take legal action if someone infringes on their copyright.

Another example is a writer who wants to publish a book. They must register their work with the Copyright Office and send two copies of the book to be included in the copyright catalog. This ensures that their work is protected and that others cannot use it without permission.