How does a ventriloquist dummy work?

a ventriloquist dummy es a opening in it's back that the audiance cant see. there are many strings that the ventriloquist can pull to make the puppets mouth open, raise it's hand, or even roll it's eyes. It is actually very hard to master ventriloquisiom, for the ventriloquist has to learn to talk through partially closed lips while making it appear that the "dummy" is talking