D♭, or D flat, is a musical note that is one semitone lower than D. It is commonly used in various musical scales and compositions, particularly in genres like jazz, classical, and pop. In the context of the piano, D♭ is played by pressing the black key immediately to the left of the D key. In terms of music theory, D♭ can be found in several key signatures, including B♭ major and G♭ major. It is also the enharmonic equivalent of C♯, meaning they sound the same but are notated differently. Understanding D♭ is essential for musicians when reading sheet music and performing.