Downoad datasheet here.

A relay is an electrically operated switch. Many relays use an electromagnet to mechanically operate a switch, but other operating principles are also used, such as solid-state relay. Relays are used where it is necessary to control a circuit by a low-power signal (with complete electrical isolation between control and controlled circuits), or where several circuits must be controlled by one signal.

Features:

Easy to use with bread board

5V operated

Tutorial Available with arduino – http://goo.gl/8Xmf4X

• An electromechanical switch.
• Operates at 12 V.
• Useful for switching AC or DC devices.
• PCB mountable.