This is a Vibration DC Motor that generates Vibrations when required in your projects. This is the kind of motor that is used in cell/mobile phones to generate vibrations when an incoming call comes in. Vibration effect is can be used to give feedback to the user when some event happens in your project. e.g. when a user presses a button the user feels vibrations. With this user is certain that his action (pressing button) was accepted by the project. This is also called Haptic Feedback.