The Arduino is a simple little device that looks like this:
Despite the fact that it fits nicely in one hand, don’t be fooled—there’s quite a bit of functionality crammed into that small space. On the left side, there’s a USB port that allows the Arduino to communicate with your laptop or desktop computer. Just plug it the USB cable into the Arduino and plug the other end into your computer. Most computers will auto-recognize any USB device, and the Arduino is no exception.
Key Positions on the Arduino Diecimila Board