The on-board ATmega328 receives data over multiple digital interfaces (such as TWI, UART and SPI) and does all the PWM and upkeep of the display so your main controller doesn’t have to. There are even two built-in functions that can be activated with solder jumpers.
The on-board graphic OLED matrix can display waveforms, measurements and menu systems. You can also connect it to your PC and use Gabotronics' XScopes software to control the device and view waveforms.
Three linear slide potentiometers connected to the Arduino’s analog pins 0 through 2. Red and yellow LEDs connected to digital pins 5 and 6 - PWM pins - so you can easily vary their brightness. Three momentary push buttons connected up to the Arduino’s digital pins 10 through 12. Those lines will go low when the buttons are pressed.