The Arduino Uno is a microcontroller board based on the Atmel's ATmega328
It has 14 digital input/output pins (of which 6 can be used as PWM outputs) and 6 analog inputs
The Arduino Uno can be powered via USB connection or with an external power supply
It contains everything needed to support the microcontroller; simply connect it to a computer with a USB cable (not included)
Arduino IDE supports Windows, Mac OS X or Linux