Music theory is the study of how music works. It is the set of principles, rules, and concepts that explain how music is created and organized. It includes things like rhythm, melody, harmony, form, and notation.

Music theory can help musicians understand why certain chords and melodies sound good together, how to create a melody that is memorable and catchy, and how to structure a song or piece of music. It can also help musicians communicate with each other, by providing a shared language and set of concepts.

Overall, music theory provides a framework for understanding and creating music, and can be a valuable tool for musicians of all levels and styles.