Geometry Points
A point is a position in space defined by 3 coordinates: X, Y, and Z.
All geometry should have at least one point, otherwise the geometry wouldn't exist in space.
Geometry doesn't require any of the other structures such as attributes or primitives. If a geometry only has points, it would render as point sprites, like particles.
Primitives define references to points as "vertices". Multiple vertices may reference the same point.
Attributes define the other properties of a point used by geometry, such as surface normals and texture coordinates.