Its 4-pole configuration (4P) switches all three phases and the neutral, though the neutral conductor is not switched internally — the 4th pole is a switched pole, not a solid neutral bar.
Rated 40 A at 400 V AC — this breaker protects a 40 A feeder or load circuit on a 400 V three-phase system (common European 230/400 V networks). If your panel's fault level is higher (e.g., industrial substations), you need a higher-rated MCB or an upstream current-limiting fuse. The C curve is the default for general-purpose loads; for purely resistive loads or long cable runs, a B curve would be more sensitive, while D curve suits high-inrush welding or drive inputs. Conductor termination accepts solid or stranded wire from 0.75 mm² up to 25 mm² via screw terminals torqued to 2.5–3 N·m. That range covers everything from a 1.5 mm² control circuit to a 25 mm² main feeder — no adapter lugs needed for the larger sizes. The 4-pole width is 4 width units (72 mm,), so it occupies four 18 mm module spaces on a DIN rail.