The Arduino Leonardo is a development board based on the ATmega32u4. The board contains 20 digital input / output pins (7 of which can be used as PWM outputs and 12 as analog inputs), a 16 MHz crystal and a micro USB connection. Connect the sign to the computer and you can start immediately.
The Leonardo differs from previous boards in that the ATmega32u4 contains built-in USB communication. This means that only a single microprocessor is required on the board. An additional advantage is that this board can be used as a mouse or keyboard (for example for brute forcing). Because the USB communication goes through the main chip, the Arduino will log off and log on to the computer when you program or reset it.
This arduino is a clone, which means that this sign is not built in the original factory. The only difference between original and clones is that these Arduinos are cheaper. All components and circuits are otherwise identical.