When you depress your brake pedal, your car transmits the force from your foot to its brakes through a fluid. Since the actual brakes require a much greater force than you could apply with your leg, your car must also multiply the force of your foot.

Brake pads do not last forever and gradually they will wear out. This means that they will need to be replaced. Brake pads should be inspected on a regular basis and they should be replaced as soon as they have worn down to their minimum, or when a brake warning light appears on your dashboard.

Brake discs need to be replaced every so often. It is a good idea
to check them every time you check your brake pads. If you have noticed your car pulling to one side when you brake or even making a noise, then it may be time to replace your brake discs.

Brake fluid needs to be changed too. Moisture is absorbed into
the fluid through brake hoses and rubber seals and, eventually,
the fluid will have to be replaced when the water content becomes too high.

GSF Car Parts sell an electronic tester too measure moisture content. New fluid should always be stored in a sealed container
to avoid moisture intrusion.