A piano chord is a combination of three or more notes played simultaneously on a piano. Chords are the building blocks of music, providing harmony and depth to melodies. The most common types of chords include major, minor, diminished, and augmented, each creating a different emotional effect. Chords are typically named after their root note, which is the lowest note in the chord. For example, a C major chord consists of the notes C, E, and G. Musicians use chords to accompany singers or other instruments, making them essential for creating a full sound in various musical genres.