Geometry animations are used in master scenes. The animation itself is identical to an animation which is created for a standalone scene. Geometry animations are subject to the master scene, which dictates when the animation of the object scene starts through the AO and BO directors. The geometries in the master scene are typically used as backplate graphics. Text or images would then be added on top of the backplate by the object scene.
The example below shows a lower third master scene, with animated geometries that form a simple lower third backplate: