It can be used as a small arduino 32u4 (with 8 digital and analog pins) or, with the addition of the 6 pin boxed header and the switch, it can be used as a programmer. In programmer mode D10 is routed to the "reset" pin of the 6 pin header so it can program other Arduinos. In normal mode the reset pin of the 6pin header is routed to the reset of the micro just like the normal ICSP of the Arduino UNO. In normal mode a bootloader can be burned onto the 32u4. I also had the idea that this could be used to "prank" someone else's computer by having the micro randomly move the mouse a few inches or open "phantom" programs and write "ghost" messages or make the person think their computer has been hijacked.