The Arduino UNO R3 is a microcontroller board based on the ATmega328 AVR microcontroller. It has 20 digital input/output pins (of which 6 can be used as PWM outputs and 6 can be used as analog inputs).  Programs can be loaded on to it from the easy-to-use Arduino Integrated Design Environment (IDE) , a FREE download.  The Arduino has an extensive support community, which makes it a very easy way to get started working with embedded electronics. The R3 is the third, and latest, revision of the Arduino UNO.

There are several versions of the Arduino UNO R3.  We will explain each of them here:
Original: Removable DIP ATMEGA328P micro-processor, and ATmega16U2 serial converter.  Assembled in Italy.
Original SMD: Non-removable ATMEGA328P-AU micro-processor, and ATmega16U2 serial converter.  Assembled in Italy.
Clone: Removable DIP ATMEGA328P micro-processor, and ATmega16U2 serial converter.  Assembly varies.
Clone SMD: Non-removable ATMEGA328P-AU micro-processor, and ATmega16U2 serial converter.  Assembly varies.
Compatible: Removable DIP ATMEGA328P micro-processor, and CH340 serial converter.  Assembly varies.
Compatible SMD: Non-removable ATMEGA328P-AU micro-processor, and CH340 serial converter.  Assembly varies.

TECHNICAL DETAILS
UNO Type: Clone
Power: USB or External Power Supply
User I/O Lines: 20
PWM Outputs: 6
Analog Inputs: 6
Ground Access Points: 4
USB Connector: B
Input Voltage DC: 7-12V