The ii-V-I progression is a fundamental sequence in jazz and popular music, consisting of three chords: the minor second (ii), the dominant fifth (V), and the tonic (I). This progression creates a strong sense of resolution, making it a favorite among composers and improvisers alike. In the key of C major, for example, the ii chord is D minor (Dm), the V chord is G major (G), and the I chord is C major (C). Musicians often use this progression to build tension and release, allowing for expressive melodies and harmonies in their compositions.