Accidentals are musical symbols that alter the pitch of a note. The most common accidentals are the sharp (♯), flat (♭), and natural (♮) signs. A sharp raises a note by a half step, while a flat lowers it by a half step. A natural cancels any previous accidentals, returning the note to its original pitch. Accidentals can appear in various musical contexts, such as in sheet music or during a performance. They are essential for creating different scales, harmonies, and melodies, allowing composers and musicians to express a wide range of emotions and styles in their work.