The majority of cars come with disc brakes in the front, and many have disc brakes in the rear. There is a part of the disc brake system called a calliper. The brake fluid travels from the master cylinder to the callipers when you press the brake pedal. Brake fluid then applies pressure on the piston inside the calliper, pushing the brake pads against the rotors to slow/stop your car. A car can have either 2 or 4 callipers. If the vehicle has rotors on all four tires, then it will have four callipers. If the vehicle has two rotors and two drums, it will come with two callipers in front. The callipers can become contaminated, rusty, and start to leak brake fluid. Brake callipers absorb a lot of heat generated from the braking system. Over time, this heat can destroy or weaken the seals inside the callipers. Calliper servicing is usually done as part of a brake service job.
Work on brake callipers would likely include new brake pads because if the callipers have gone bad, it is very likely that the brake pads are worn out.
Remove and replace brake calliper and pads. Inspect brake rotors. Inspect brake line hoses. Replace brake fluid. Re-check brake system for fluid leaks. Bleed the brake system. Torque wheels to factory specifications. Check brake system performance.
All services associated with the proper function of your brakes are essential. In addition to safety issues, ignoring small repairs can quickly lead to more serious (and more expensive) problems.