[Product Information]

ATmega328P onboard chip in QFN package running at 3.3V logic 12MHz clock rate, 28K FLASH available
USB bootloader with a nice LED indicator looks just like a USBtinyISP so you can program it with AVRdude and/or the Arduino IDE (with a few simple config modifications). Also has headers for an FTDI port for reprogramming
Micro-USB jack for power and/or USB uploading, you can put it in a box or tape it up and use any USB cable for when you want to reprogram. On-board 3.3V power regulator with 150mA output capability and ultra-low dropout. Up to 16V input, reverse-polarity protection, thermal and current-limit protection.
Power with either USB or external output (such as a battery) - it'll automatically switch over
On-board green power LED and red pin #13 LED Reset button for entering the bootloader or restarting the program.