I like to correct a few here when brakes are applied initially the front brakes are activated on low pressure as the force on the brake padel is increased the rears come in to action also. The reasoning behind it is that if all four brakes were to be activated at equal force the rears would lock up due to their not being any load on them since all or most of the load is transferred to the front wheels. The rears would lock and send the car into a spin and loose control or make it sideways and tip over.
If you like to learn about your car try it just rasing the handbrake up a couple or few clicks (depending how worn out your rear pads are) you will notice the breaking force or stopping distance would be shortened and if your were to raise it another couple clicks enough so the rear pads are bearly touching you would see that during braking the rear end would want move forward.
There are lot of reason for it maybe I will explain later.