A more thorough explanation:

Joint authors are two or more people who work together to create a piece of work that can be copyrighted. Each author contributes to the work and intends for their contribution to be combined with the others to create a single work. They can each use the work as they wish, but they must share the profits with the other authors.

Two musicians collaborate on a song. One writes the lyrics and the other composes the music. They intend for their contributions to be merged into a single work, and they both have the right to use the song as they wish. If the song makes money, they must share the profits.

Two authors write a book together. One writes the first half of the book, and the other writes the second half. They intend for their contributions to be merged into a single work, and they both have the right to use the book as they wish. If the book makes money, they must share the profits.

These examples illustrate joint authors because in both cases, two or more people work together to create a single work that they can each use as they wish. They must share the profits because they are joint authors and each contributed to the work.