Also known as burbles, it’s a feature from the calibration of the car that allows a misfire (specifically targeted) that happens when the driver lifts off the throttle. Thus, one of the main ways in which this feature is obtained is by modifying the ignition map, altering the specific timing feature on it. This is done to set up the ignition, timing it to produce its maximum power.
Pops and bangs are the sound of the explosion’s echo in the exhaust. When timed correctly, the valve in the exhaust will open to allow gas (along with the well-known sounds) to get out.