A usual brake job includes replacing the brake linings (new disc brake pads and shoes), resurfacing the rotors and drums, adding new brake fluid, bleeding the system, and inspecting/replacing any additional damaged components. If rotors or drums are worn out or past safe limits, they cannot be resurfaced and have to be replaced. Leaky disc brake calipers, drum brake wheel cylinders or the master cylinder ought to be rebuilt or replaced.
Having your brakes done is a very important thing to do on any vehicle. Your brakes can go out at any time, so if you suspect that your brakes are starting to get worn out, either have your mechanic fix them or do it yourself. Having your brakes wear down can cause damage to other parts of your car, as well. Then you are going to have to fix more than just your brakes. By not fixing your brakes, you can injure yourself or other people as well. So, next time you are sitting in traffic and your brakes start making a squealing noise, then its time to take your car in and have the brakes looked at. Brake fluid should be changed at least once a year to keep it fresh and clean.