The C-curve means it holds up to 5–10× rated current momentarily, so it won't nuisance-trip on motor inrush or capacitor bank charging, but clears fast on a hard short.
Thermal derating — the real-world rating
The 25 A nameplate rating is at 30 °C. Inside a warm panel at 40 °C it's good for 24 A; at 50 °C it drops to 23 A; at 60 °C it's 22 A; at 70 °C it's 21 A. If your BOM line calls for 25 A continuous in a 50 °C enclosure, this part won't hold — you'd need to step up to the next frame or ventilate the panel. The derating curve is linear enough to interpolate between the published points.
Mounting position is any orientation. The IP20 rating applies once the distribution board is installed with conductors connected; the front face is finger-safe but the terminals need enclosure protection.