A more thorough explanation:

The Berne Union is a treaty alliance of countries that are members of the Berne Convention. The Berne Convention is an international agreement that sets out rules for the protection of literary and artistic works, such as books, music, and paintings.

The Berne Union was established to promote international trade and investment by providing a framework for the protection of intellectual property rights. Members of the Berne Union work together to ensure that the rights of creators and owners of intellectual property are respected and protected in all member countries.

For example, if a musician from one Berne Union country creates a song, that song is automatically protected by copyright in all other Berne Union countries. This means that the musician can control how the song is used and can receive payment for its use in other countries.