The 6 kA breaking capacity (per both EN 60898 and IEC 60947-2) tells you it can safely interrupt a fault current up to 6 kA at 400 V AC without welding or arcing over. That's the standard residential and light commercial rating; if your panel's prospective short-circuit current exceeds 6 kA, you need a higher-rated breaker upstream. Frequency is 50/60 Hz.
Panel integration and environment
Snap-on DIN-rail mount, 3 MW units wide. Halogen-free and silicon-free construction — no corrosive off-gassing if the breaker arcs internally.
Mechanical and electrical endurance
Typical mechanical service life is 20 000 operating cycles — that's the handle being switched on and off under no-load.