Final answer:
Frets are the pieces of gut wrapped around the neck of a lute to mark off each semitone. They act as a guide for the musician to accurately play different notes on the instrument.
Step-by-step explanation:
The pieces of gut wrapped around the neck of a lute to mark off each semitone are called frets. Frets act as a guide for the musician to accurately play different notes on the instrument. By pressing down on the frets, the length of the vibrating string is shortened, changing the pitch of the sound produced.