A brake caliper is a crucial component of a vehicle's disc brake system. It is a hydraulic device that houses the brake pads and pistons. When the driver presses the brake pedal, hydraulic fluid from the master cylinder is transmitted through the brake lines to the calipers. This causes the pistons within the calipers to extend, pushing the brake pads against the spinning brake rotors.

The resulting friction between the brake pads and rotors converts the vehicle's kinetic energy into heat, thereby slowing down the vehicle or bringing it to a halt. In short, the main function of the brake caliper is to apply force to the brake pads, generating the necessary friction to stop the rotation of the wheels and enable the vehicle to decelerate or stop safely.