Uno R3 - compatible with Arduino Uno R3 board. Built on the Atmel ATmega328 microcontroller and USB-UART interface chip CH340G. Board for functionality similar to the Arduino Uno (ATmega 168/328). It is a budget, but the same stable, and uses the original chips Atmel ATmega (16 MHz). The board used the chip CH340G as converter UART-USB. Chip CH340G - is a budget solution. When you work in the frequency 12Mhz, giving a stable result of data exchange (need install drivers to computer). Uno R3 - connects to the computer via micro USB cable (used for almost all Android smartphones).
You can supply power to board through the Micro USB connector or DC-jack. The voltage regulator (LDO) can deal with incoming voltage from 6V to 12V DC. Output current for 5V - about 800mA, for 3.3V - about 180mA (Please note that the higher the input voltage the lower the outgoing current). That will provide a reliable power most of your initial projects. We recomiende supply 7-9V.