There are many advantages to hydraulic disc brakes on a bicycle. Unlike rim brakes, discs have tremendous stopping power in mud, rain and snow, and they can also be used with any tire width. They are available in mechanical and hydraulic. Hydraulics tend to cost more but have more stopping power. Because you're using fluid as opposed to a cable pulling system, braking tends to be fast and efficient. Once hydraulic brakes are installed on your bike, you will need to adjust them to ensure they are set up properly and to your riding preference.
Place the bike in the bike stand.
Check the brake lever. It should be positioned horizontally to the handlebar, in a position that is easy for you to reach. To avoid tweaking the lever in a crash, you should rotate it down so that it's not level with the handlebar, but just below it. Use a hex wrench to loosen the bolts as you move the brake levers to the proper position.
Align the brake calipers. It's important to position the calipers so that they do not hit the spinning rotor. This causes drag and sometimes a howl or a rubbing sound when the caliper alignment is off.
Spin the wheel of the brake you are adjusting. Watch how the rotor spins in between the calipers. It should be centered. If it is rubbing, use a hex wrench to loosen the two centering bolts that hold the caliper to the mounting bracket.
Pull the brake lever gradually and tighten the bolts. If you're having trouble centering the rotor, try slipping a thin business card in between the rotor and the pads before pulling the brake.
Spin the wheel and eye the disc and calipers to ensure the rotor is centered and not rubbing.
Take the bike for a test spin. Gradually apply the brakes several times to break in the rotors. Check that the brake levers are in a comfortable position, that the rotors aren't rubbing and that the bike is braking efficiently.