I need someone to explain this to me.

RepRap Motherboard

reprapmb-1

When the RepRap team found themselves pushing the limits of the Arduino, they started looking for alternatives. They found it in the ATMega644P. It has four times the memory and four times the RAM compared to the ATMega168 used in the standard Arduino. It also has 32 I/O pins. They ported the Arduino software to the microcontroller and started producing Sanguino boards. Now that the base design is nailed down, they’ve begun expanding it to their specific purpose. Pictured above is a prototype RepRap motherboard. While the Sanguino is barebones, this board has onboard connectors for all of the RepRap’s motors, so you can just plug it in. It is also designed to support the future Generation 3 electronics. Probably the most interesting feature is the SD card slot. The goal is to eventually have a board that can run the RepRap without a host computer if necessary; it will manufacture designs directly from the flash card.