Source PIc :- Howstuffworks
Most of us do not know how to choose disc brake pads because to select it you must have some knowledge about it.
What is Disc Brake
The disc brake or disk brake is a device for slowing or stopping the rotation of a wheel. A brake disc usually made of cast iron or ceramic composites (including carbon, Kevlar and silica), is connected to the wheel and/or the axle. To stop the wheel, friction material in the form of brake pads (mounted on a device called a brake caliper) is forced mechanically, hydraulically, pneumatically or electromagnetically against both sides of the disc. Friction causes the disc and attached wheel to slow or stop. Brakes (both disc and drum) convert friction to heat, but if the brakes get too hot, they will cease to work because they cannot dissipate enough heat.
source info :- wikipedia.com
How to change your disc brake pads.
1. Raise your vehicle and secure it on jack stands. Remove the wheels, only after the car is safely secured on the jack stands and the back wheels are blocked. Open the hood of the car and remove the cap to the brake fluid reservoir.
2. Remove the bolts keeping the caliper secure, and slide it away from the rotor and brake pads.
3. Remove the bolts or clips securing the brake pads and remove the pads on either side of the rotor. If grooves are found on the rotor, that it is a good indication that the rotor should be replaced.
4. Locate the piston along the back of the rotor, and use a c-clamp to move the piston in order to accommodate the new brake pads.
5. Lubricate the back of the new brake pads on the side that will be touching the rotor and attach to the caliper using the bolts or clips. Repeat on the other side of the car.
6. Replace the cap to the brake fluid reservoir and secure the wheels back on the car before lowering the car to the ground.
7. Pump the brakes several times until normal pressure returns to the brake pedal.
Or you can watch video on how to changing the brake disc