What are the different music scale modes and how are they used in music theory?

Music scale modes are variations of the major scale that start on different notes. The main modes are Ionian, Dorian, Phrygian, Lydian, Mixolydian, Aeolian, and Locrian. Each mode has a unique sound and can be used to create different moods in music. They are used in Music Theory to create melodies, harmonies, and chord progressions that add depth and complexity to compositions.