It "beds" the brakes. In reality your brakes work best when the pad is pressed against a layer of pad material that gets deposited on the rotor. It takes heat to make that happen. how much heat depends on the make up of the pads.
They put pretty aggressive pads on these because of the power and the weight. If you drive lightly with these pads they don't deposit the material on the rotor and you get pad to metal contact. Which squeals because these have semi metallic pads i.e. little slivers of metal in the pad to help transfer heat.
Bedding in the pads transfers pad material but as you drive around afterwards they will scrub the rotors back down so you'll have to do it occasially or drive like a crack head.
If you'd like to know more Stoptech has a good article:
http://stoptech.com/technical-suppor...ake-pad-bed-in