All modern brakes are hydraulic. This means your brake pedal presses a piston inside a cylinder. This applys pressure on the fluid in the cylinder. (brake fluid) .

This cylinder which is on the end of the brake pedal is called the "master cylinder".

The pressurized fluid from the master cylinder (fluid doesn't compress, so it's almost like a solid linkage) is carried equally to all wheels, which have "slave cylinders."

There are 2 basic kinds of common brakes: disc and drum.

Drum brakes are older, and use two half moon shaped "brake shoes" which are pressed outwards agaist the inside of the "brake drum" by the "slave cylinders", which are called "wheel cylinders". These brake are found on the rear of most vehicles, and on the front of some new and most older vehicles. (pre 1980)

Disc brakes have a "caliper" for the "slave cylinder", and the caliper presses disc brake pads against both sides of the flat brake rotor.