Two kinds
A vase, and a cube
Not every ambiguous figure works in quite the same way, even when both can flip.
The vase and the faces
The figure-ground illusion is commonly experienced in the illustration of a white vase whose outline is created by two black profiles. Britannica Scholars: illusion
Britannica Students treats the vase-and-faces figure as an example of object reversibility, an illusion also encountered in the Necker cube. Britannica Students: illusion
The Necker cube
Another example of ambiguity and object reversibility is the Necker cube, which may seem to flip-flop. Britannica Scholars: illusion
The percept of a three-dimensional wireframe cube is already an interpretation, performed on the two-dimensional visual input of a flat line image. Michael Bach: Necker cube
Britannica Scholars presents the vase as a figure-ground illusion, and the Necker cube as another example of ambiguity and object reversibility. We have not pushed that into a stricter taxonomy than the sources support.
The hollow face is a three-dimensional case: a real mask, or a film of one, rather than a flat outline.