Performed by an instrument called an articulator. It mimicks the movements of the jaws. E.g. Whipmix articulator, Denar articulator.
Used by dentists to articulate study models of their patient's teeth in the correct relationship - ie the relationship between the upper jaw, the lower jaw and the jaw joint.
Impressions of the patient's teeth are taken and study models made of them. These study models are then mounted on the articulator with dental plaster. The correct position of the models, or casts, are determined by a wax bite record.

It is used so that the dentist can play with the arrangement of your teeth with out your cheeks, lips, throat and tongue out of the way.