What's the difference between a parking brake and a service brake?

What's the difference between a parking brake and a service brake?

The parking brake is the brake that is designed to "hold" the vehicle.
The service brake is the system that is designed to slow down the vehicle and bring it to a stop. Parking brakes are also referred to as "emergency" brakes although , in an emergency they would never slow down a vehicle in a safe manner.
The service brake is activated every time you step on the brake pedal and it distributes the braking force hydraulically to the front and rear wheels. 75% front and 25% rear, on average.
The parking brake is typically cable operated and applies force to either dedicated brake shoes inside the rear rotor or, through the piston in the calliper. It can be operated by a separate pedal or a hand lever, usually located between the front seats. Electric parking brakes have a switch as in newer vehicles with electric actuators on the rear wheels. (electric parking brakes are a very bad idea btw!) Some SAAB models of the eighties and nineties had the parking brakes acting on the front wheels.