the study of geometrical properties and spatial relations unaffected by the continuous change of shape or size of figures.
the way in which constituent parts are interrelated or arranged.“the topology of a computer network”
Topology on a 3D model is basically what makes the model. There’s bad topology and good topology. All of the shapes on a 3D mesh should have no more and no less than 4 sides. Also, they should all be a good enough shape to allow the face for proper movement when in the game. It needs to have an edge flow which means that if you draw a line through the mesh it will have no trouble coming out of the parallel side of the topology.