It's a 3-pole unit rated 20 A at 40 °C, with a breaking capacity of 75.6 kA at 415 V AC — enough to handle heavy fault currents on a 400 V class feeder without cascading upstream. The built-in undervoltage release (UVR) lets you trip the breaker on loss of control voltage, which is handy for emergency-stop circuits or mains-supervision schemes.
The 3VA1020-4ED36-0DA0 fits a standard 76.2 mm wide (3-inch) DIN cutout, 130 mm tall, 70 mm deep. The TM210 thermal-magnetic trip unit is fixed, so there's no interchangeable trip to order separately; it's a straight drop-in for a 20 A feeder.