A cadence is a sequence of chords — usually at the end of a phrase — that provides a sense of pause, resolution, or closure. Just as punctuation shapes the flow of language, cadences shape the flow of music, marking the end of musical thoughts or sections.
Cadences are especially important for reinforcing the tonal center of a song. Most cadences return to the I chord, often after a moment of tension that makes the resolution feel satisfying. The chord that precedes the I in a cadence is sometimes called a cadence chord, denoted by "C" below:
In popular music, the most common cadence chord is the V, as shown below in Tom Petty's Free Fallin'. This motion — from dominant to tonic — creates a strong sense of arrival and is often used at the end of verses, choruses, or to link two different sections.