Arduino is an open-source electronics
platform based on easy-to-use hardware and software. Arduino boards
are able to read inputs - light on a sensor, a finger on a button, or
a Twitter message - and turn it into an output - activating a motor,
turning on an LED, publishing something online. You can tell your
board what to do by sending a set of instructions to the
microcontroller on the board. To do so you use the Arduino
programming language (based on Wiring), and the Arduino Software
(IDE), based on Processing.