The ABB S802S-D20 is a 2-pole miniature circuit breaker rated 20 A continuous with a Trip Curve D characteristic. That D-curve means it's designed to hold through the high inrush current of motor starts, transformer energization, or other inductive loads — the magnetic trip threshold is 10 to 20 times rated current, so it won't nuisance-trip on a 3-phase motor bank or a control transformer. The 50 kA interrupting rating at 230 VAC tells you it can safely clear a bolted fault up to that level without welding contacts or cascading failure upstream — important for high-fault-capacity panels where standard 10 kA MCBs would need a current-limiting fuse ahead of them.
The 2-pole format covers 230 VAC line-to-line or a split-phase circuit where you need both poles switched.