Arduino is an open-source physical computing platform based on a simple i/o board and a development environment that implements the Processing/Wiring language. Arduino can be used to develop stand-alone interactive objects or can be connected to software on your computer (e.g. Flash, Processing, MaxMSP). The open-source IDE can be downloaded for free (currently for Mac OS X, Windows, and Linux).
The Arduino Nano is a small, complete, and breadboard-friendly board based on the ATmega328 (Arduino Nano 3.x) or ATmega168 (Arduino Nano 2.x). It has more or less the same functionality of the Arduino Duemilanove, but in a different package. It lacks only a DC power jack, and works with a Mini-B USB cable instead of a standard one.
The microcontroller (an ATmega328) on the Arduino Nano is a physically smaller version of the chip on the USB Arduino boards.
• ATmega328 microcontroller.
• Input voltage - 7-12V.
• 14 Digital I/O Pins (6 PWM outputs).
• 6 Analog Inputs.
• 32k Flash Memory.
• 16 Mhz Clock Speed.