Classic Mega 2560 - compatible with Arduino Mega 2560 board. Built on the Atmel ATmega2560 microcontroller and USB-UART interface chip Prolific PL2303(16MHz).
Board for functionality similar to the Arduino Mega 2560, and uses the original chips ATmega2560 (16 MHz).
Classic Mega 2560 - connects to the computer via USB-B (classic of Arduino).
You can supply power to board through the USB-B connector or DC Barel Jack power connector. The voltage regulator (LDO) can deal with incoming voltage from 6V to 12V (peack 18V) 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.