A chord progression is a sequence of chords played in a piece of music. Chords are groups of notes that sound harmonious together, and they form the foundation of a song's structure. Different progressions create various emotions and styles, influencing how the music feels to the listener. Common chord progressions, like the I-IV-V or ii-V-I, are widely used in many genres, including pop, rock, and jazz. Musicians often experiment with these progressions to create unique melodies and harmonies, making them essential for songwriting and composition.