This is how wikipedia defines Arduino:
Arduino is a popular open-sourcesingle-board microcontroller, descendant of the open-source Wiring platform, designed to make the process of using electronics in multidisciplinary projects more accessible. The hardware consists of a simple open hardware design for the Arduino board with an Atmel AVR processor and on-board input/output support. The software consists of a standard programming language compiler and the boot loader that runs on the board.
Arduino hardware is programmed using a Wiring-based language (syntax and libraries), similar to C++ with some slight simplifications and modifications, and a Processing-based integrated development environment.
Current versions can be purchased pre-assembled; hardware design information is available for those who would like to assemble an Arduino by hand. Additionally, variations of the Italian-made Arduino—with varying levels of compatibility—have been released by third parties; some of them are programmed using the Arduino software.
More information about the video from TED :
Massimo Banzi helped invent the Arduino, a tiny, easy-to-use open-source micro controller that’s inspired thousands of people around the world to make the coolest things they can imagine — from toys to satellite gear. Because, as he says, “You don’t need anyone’s permission to make something great.”