This corresponds to the camera being in the same space as, and moving under the same set of transformations as, the geometry itself. In Euclidean space Virtual is the most useful model. In hyperbolic space, the Projective model setting gives a view of the projective ball model of hyperbolic 3-space imbedded in Euclidean space. The camera is initially outside the unit ball. In this model, the camera moves by Euclidean motions and geometry moves by hyperbolic motions.
Conformal model is similar but shows the conformal ball model instead.
Spherical motions give rise to projective transformations in the Projective model, and to transformations in the Conformal model. In both of these models the camera moves by Euclidean motions. In Projective and Conformal models, the unit sphere is drawn by default. You can turn it off and on at will using the Draw Sphere button in the Camera panel. In the Conformal model, polygons and edges are subdivided as necessary to make them look curved.