A more thorough explanation:

Copyright notice is a legal way to inform people that a published work is protected by copyright law. It includes basic information about the copyright owner and the year the work was first published. The purpose of a copyright notice is to let people know that the work is copyrighted and who owns the rights to it.

For example, if you write a book and want to protect your rights as the author, you can include a copyright notice on the title page. The notice might look like this:

© 2022 John Smith

This notice tells readers that the book is copyrighted and that John Smith is the owner of the copyright. It also shows the year the book was first published.

Before 1989, a copyright notice was required for all published works. But now, according to the Berne Convention, it is no longer necessary for works published after March 1, 1989. However, if a work was published before that date, it still needs a copyright notice to be protected by copyright law.

A copyright notice should include the copyright symbol (©), the name of the copyright owner, and the year the work was first published. It should be clearly visible and easy to read.