This is a popular 20×4 lcd display. It is based on the hd44870 display controller which makes it is easy to interface with most micro controllers. Its extreme popularity ensures that no matter which micro controller platform you are using this lcd on, you will definitely find ready libraries to use this lcd.
It works of 5v and has a green back light which can be switched on and off as desired. The contrast of the screen can also be controlled by varying the voltage at the contrast control pin.