Originally Posted by m3flyer
...vented points to the area in between the inside disc surface (where the inner pads touch) of the rotor and the outside (where the outer pads touch) surface.
If you stand a rotor on end and look at it as if it were a "blade", the vented area is the space in between the inner and outer surfaces.
Non-drilled rotors can be vented (space in between surfaces with vanes to guide the air through) or non-vented (solid). Either of these then can be cross-drilled or slotted.
That is all...
Correct. Contrary to popular belief, the holes or slots on the surface are not for cooling the rotors. They are for dissipating the boundary layer of gases that build up between the pad and rotor, hence maximizing braking power.