Harmony refers to the combination of different musical notes played or sung simultaneously to create a pleasing sound. It enhances the melody by adding depth and richness, often using intervals and chords to achieve this effect. Chords are specific groups of notes, typically three or more, that form the basis of harmony. Chords can be major, minor, diminished, or augmented, each conveying different emotions and atmospheres. In music theory, harmony is essential for creating structure and progression within a piece, allowing composers to evoke feelings and support the main melody. Understanding harmony and chords is fundamental for musicians and composers alike.