It’s an Arduino shield that adds a Linux SoC, WiFi, Ethernet, and USB Host to any Arduino board from the Uno, to the Duemilanove and Mega.

Yes, two AA batteries at 1.5v each would equal only 3 volts when connected in series. The Arduino needs 5v so [AI] decided to use a MAX756 DC-to-DC step-up regulator to maintain a steady stream of 5v.