Scale
The D♭ major scale has 7 notes: D♭, E♭, F, G♭, A♭, B♭, C. Its enharmonic twin is C♯ major. Hear it, see it on the keyboard and find the chords that belong to it.
5 flats: B♭, E♭, A♭, D♭, G♭
Roman numerals show each chord's degree in the key. Upper-case is major, lower-case minor, ° diminished.
The major scale follows the step pattern W W H W W W H. It is the basis of Western tonal harmony, and every major key has a relative minor that shares its notes and key signature.
Use the Scale & Chord Finder to look up any other root or mode.