Starting the major scale on each of its seven notes gives seven modes: Ionian (major), Dorian, Phrygian, Lydian, Mixolydian, Aeolian (natural minor) and Locrian.
Each has a characteristic sound. Dorian is minor with a brighter sixth, common in funk, jazz and Celtic music. Phrygian has a dark flat second, heard in flamenco and metal. Lydian has a raised fourth that sounds dreamy and is often used in film scores. Mixolydian is major with a flat seventh, common in rock and folk.
Using it in a prompt
Ask for a mode to get a specific colour: "Lydian, dreamy and floating" or "Phrygian, dark and tense". It is a more precise instruction than "happy" or "sad".