The types of servo motors that we will use with the Arduino are pretty small, but most have fairly high torque and are very energy efficient. This allows us to use these motors for industrial-grade applications such as robotic arms, conveyor belts, autofocus lenses in cameras and even solar-tracking systems for solar panels.
A servo motor is made up of a DC motor, which does the actual work; a potentiometer, which controls the amount of power going to the motor; control circuitry, which controls the movement of the motor and gears. The following photograph shows a servo motor connected to a robotic claw:
A servo motor contains three wires for the control signal, power and ground. The signal wire is usually orange or yellow. The power is the usual red, and the ground wire is usually brown or black.
Some smaller servo motors can use the 5V out on the Arduino...