What is Arduino?

Recently, I heard about Arduino from my team mate and got it by online. Arduino is open source platform. I had only heard about open source programming not hardware. You guys can get detailed information from this. 

Arduino Team 

Team Arduino: Gianluca Martino, Massimo Banzi, and David Cuartielles        Photo: James Day 

Ohh open-source always smells like freedom (yay :p). My team mate explained and suggested me to learn about Arduino. So I planned to make little project because I used to want to do something with microcontroller board. It seems very interesting.