The UNO is an for Arduino compatible board. It is based on for Arduino UNO Rev3 design. Some visible improvement on hardware make more flexible and easier to use. SPI, COM and IIC bus breakout make bus connect easier. The for Arduino Uno Rev3 is a microcontroller board based on the ATmega328 (datasheet). It has 14 digital input/output pins (of which 6 can be used as PWM outputs), 6 analog inputs, a 16 MHz crystal oscillator, a USB connection, a power jack, an ICSP header, and a reset button. It contains everything needed to support the microcontroller; simply connect it to a computer with a USB cable or power it with a AC-to-DC adapter or battery to get started.
The Uno R3 also adds SDA and SCL pins next to the AREF. In addition, there are two new pins placed near the RESET pin. One is the IOREF that allow the shields to adapt to the voltage provided from the board. The other is a not connected and is reserved for future purposes. The Uno R3 works with all existing shields but can adapt to new shields which use these additional pins.
For 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. For 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).
1 x For Arduino UNO R3 PLUS Sensor I/O Shield Atmega328P Atmega16U2 Expansion Multifunctional Microcontroller Development Board