In order to offer you the best Arduino deals some of our boards use the CH340G chipset (if explicitly stated) instead of the Atmel AVR ATmega16U2. This controller is used to convert signals from USB to the serial port of the microcontroller. It is only used for the communication between Arduino and your computer and does not influence the performance of your Arduino.
We recommend you to install the suitable chipset driver for your operating system if your Arduino is not detected, automatically, You can download it directly from here:

CH340G Drivers:

Operating Systems Download
Windows 98/ME
Windows 2000/XP/VISTA
Windows 7/8/8.1, 32- und 64-Bit
OS X, 32- und 64-Bit ch34xInstaller.pkg
Linux no driver needed

Please do not hesitate to contact us if you have further questions. We will gladly assist you.