Car steering operates using a 'rack and pinion' system of cogs, which turns a circular movement into a horizontal movement.
When the steering wheel is turned, the turning motion is transferred down the steering column to the pinion, which sits in contact with the rack.
When the pinion is turned, the rack moves horizontally in the direction the pinion is turning.
As the rack moves, it moves two tracking rods with it. These are attached by hinges to the steering arm, and as the tracking rods move, they force the wheels to change direction.