What is intonation on a guitar and why is it important for achieving accurate pitch and tuning?

Intonation on a guitar refers to the accuracy of the pitch of each note across the fretboard. It is important for achieving accurate pitch and tuning because if the intonation is off, the notes played higher up the neck may sound out of tune even if the open strings are in tune. Proper intonation ensures that the guitar plays in tune all the way up the neck, allowing for better sounding chords and melodies.