Ventriloquism, or ventriloquy, is an act of stagecraft

Stagecraft

Stagecraft is a generic term referring to the technical aspects of theatrical, film, and video production. It includes, but is not limited to, constructing and rigging scenery, hanging and focusing of lighting, design and procurement of costumes, makeup, procurement of props, stage management, and...

 in which a person (a ventriloquist) manipulates his or her voice so that it appears that the voice is coming from elsewhere, usually a puppeteered "dummy". The act of ventriloquism is ventriloquizing, and the ability to do so is commonly called in English the ability to "throw" one's voice.
Originally, ventriloquism is a religious practice.