The circle of fifths is a way of organizing the 12 major and minor keys around a circle. The circle begins and ends with the key of C major. Moving clockwise around the circle, each key is a perfect fifth higher than the previous key. Moving counterclockwise around the circle, each key is a perfect fifth lower than the previous key.
The white keys on a piano represent the notes of the major scale. The black keys represent the notes of the sharp and flat scales. Each key signature can be represented by a letter and a sharp (#) or flat (b) symbol. For example, the key of G major has one sharp (#F). The key of D flat major has five flats (bBb, bEb, bAb, bDb, bGb).