What's the difference between head and chest voice?

What is the difference between head voice and chest voice in a physical sense?

• What do the vocal chords do differently to produce head voice compared to chest voice.

• Answer:

  You have a head voice, a middle voice and a chest voice. A voice instructor teaches you to transition from one to the other smoothly. Your middle voice is in your throat and is called the comfort zone because that the easiest voice to use. The chest voice is where you sing in your lower register of notes. Your head tones consist of your upper register or your high notes. The higher the notes the more tension on the vocal chords, the lower the notes the less tension.