Originally posted by Neil:
The Drilled rotors are designed to allow air to pass to the surface to aid cooling and the grooves are designed to de-glaze the pad and dissipate any excess break dust

Originally posted by mr_froge:
Both cross drilled and slotted rotors serve the same function.. that of removing pad gas build up when the brakes get really hot

Originally posted by hmouta:
i thought the holes are to remove gases and the slots to improve braking cuz they cut into the pads keeping them "clean" to bite without brake fading


No.

See Wilwood FAQ: Why are some rotors drilled or slotted? and Team scR: Those poor rotors

For more brake system information try these links:

Stoptech White Papers
Grassroots Motorsports Brakes article

Cheers,
--
Terry McG