The Mega 2560 is a micro-controller board base on the CH340. It has 54 digital input/output pins (of which 15 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 need to support the micro-controller; simply connect it to a computer with a USB cable or power it with a AC-to-DC adapter or battery to get start. The Mega is compatible with most shields design for the Duemilanove or Diecimila.
The Mega 2560 is an update to the Mega, which it replaces. The Mega2560 differs from all preceding boards in that it does not use the FTDI USB-to-serial driver chip. Instead, it features the CH340 programmed as a USB-to-serial converter.
Revision 2 of the Mega2560 board has a resistor pulling the 8U2 HWB line to ground, making it easier to put into DFU mode.