This is a tiny Arduino board which uses the Atmega32u4 Microcontroller. It includes an onboard USB interface which can be used to program the board and to enable the board to be used as an USB host. With its small form-factor, it can act as a USB mouse or keyboard, which is fun for making custom computer peripherals.
This tiny little board does all of the neat-o Arduino tricks that you’re familiar with: 9 channels of 10-bit ADC, 5 PWM pins, 12 DIOs as well as hardware serial connections Rx and Tx. Running at 16MHz and 5V, this board will remind you a lot of your other favorite Arduino-compatible boards but this little guy can go just about anywhere. There is a voltage regulator on board so it can accept voltage up to 12VDC.
If you’re supplying unregulated power to the board, be sure to connect to the “RAW” pin on not VCC.
*Note: The reference to Arduino refers to the Arduino project, an open source computing platform. This is not the original Arduino board. It is only an Arduino Compatible product.