A chord progression is a sequence of chords played in a piece of music. Chords are groups of notes that sound harmonious when played together, and they form the foundation of a song's structure. Different progressions create various emotions and styles, influencing how a listener feels about the music. Common chord progressions, like the I-IV-V or ii-V-I, are widely used in many genres, including pop, rock, and jazz. These progressions help establish a song's key and can be varied to create interest. Understanding chord progressions is essential for musicians and songwriters in crafting memorable tunes.