What does a capo do for a guitar and how does it affect the instrument's sound and playability?

A capo is a device used on the neck of a guitar to change the pitch of the strings. It allows the player to play in different keys without changing the fingering of the chords. The capo can affect the sound of the guitar by making it brighter or more mellow, depending on where it is placed on the neck. It can also make the guitar easier to play by reducing the tension on the strings, making it easier to press down on the frets.