The Arduino Leonardo is a microcontroller board based on the 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 needed to support the microcontroller; simply connect it to a computer with a USB cable or power it with a AC-to-DC adapter or battery to get started. The specialty of Leonardo is that unlike UNO it has a built-in USB communication without the requirement of additional hardware, this enable the board to be used as HID devices like wireless mouse or keyboards. Along with Serial port (COM) communication it also supports Virtual CDC communication. Its operating voltage is 5V with recommended input voltage limit is 7-12V. You can use it as a replacement of Arduino Uno board if you want a greater number of Analog pins and PWM outputs with more processing power. Else you can check out Arduino Nano, Mega, pro mini etc.
 
Specifications
1.Operating Voltage: 5V
2.Current O/P at GPIO pins: 40mA
3.Flash Memory: 32KB
4.SRAM: 2.5KB
5.Clock Speed: 16MHz
6.PWM channels: 7
7.Analog Pins: 12
Additional Resources
Datasheet ATMega32u4
Getting Started with Leonardo
Joystick Game controller with Arduino Leonardo
Package contents
1×Arduino Leonardo