Here are some examples of control:
Car: Steering, brakes and accelerator allow the motion of the car to be controlled. The cooling system controls the temperature of the engine.
Aircraft: Ailerons, flaps rudder and elevators control the attitude of the plane in flight.. i.e. the tilt of the wings and the direction in which the plane points.
Robotic Arm: Hydraulic or pneumatic cylinders control the position of the robot and open and close its gripper.
In a line following robot the two motors control the steering and speed of the robot.
In an oven the thermostat controls the temperature of the oven.
In a computer a quartz crystal controls the speed of the computers clock, and the clock control the execution of all the instructions.