The Mega 2560 is an update for the Arduino Mega, which it replaces.
The board is a microcontroller board based on the ATmega2560-16AU .It has 54 digital input/output pins (of which 14 can be used as PWM outputs), 16 analog inputs, 4 UARTs (hardware serial ports), 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 Mega is compatible with most shields designed for the Arduino Duemilanove or Diecimila.
CH340G replace the Atmega 8U2/16U2
CH340G Driver Download link, please copy the link and paste in browser: http://www.5v.ru/ch340g.htm
Clock Speed:16 MHz
Flash Memory:256 KB of which 8 KB used by bootloader
Input Voltage (recommended):7-12V
Analog Input Pins:16
Digital I/O Pins:54 (of which 14 provide PWM output)