ARDUINO LEONARDO WITH HEADERS is a microcontroller board based on ATmega32u4. It has 20 digital input/output pins (of which 7 can be used as PWM outputs and 12 as analog inputs), a 16 MHz crystal oscillator, a micro USB connection, a power jack, an ICSP header, and a reset button. It contains everything you need to support the microcontroller; simply connect it to a computer with a USB cable or power it with an AC/DC adapter or battery to get started. ARDUINO LEONARDO differs from all previous boards in that the ATmega32u4 has built-in USB communication, eliminating the need for a secondary processor. This allows the ARDUINO LEONARDO to appear to a connected computer as a mouse and keyboard, as well as a virtual serial / COM (CDC) port.
If you are interested in boards with similar functionality, on Arduino you can find:
Arduino Leonardo without headers
Arduino Micro
