What do frets do on a guitar and how do they affect the sound and playability of the instrument?

Frets are metal strips on a guitar's neck that divide the fingerboard into different notes. They help players accurately press down on the strings to produce specific pitches. The placement of the frets determines the pitch of the notes played. Frets affect the sound by allowing players to create precise pitches and chords, while also influencing playability by providing reference points for finger placement and facilitating easier note production.