The Arduino Mega is a microcontroller board based on the ATmega2560. 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.
from Element 14 Community
Like its little brother, the Arduino Mega 2560 serves as a great development platform for 8-bit microcontroller projects. The additional I/O and serial ports and plentiful code space in the Mega provide significant advantages over the Uno or other previous-generation Arduino boards. What is great about the Mega, and the Arduino family as a whole, is the ability to transport your code from one hardware solution to another and even beyond to your own custom PCBs.