It's a single-function unit with a changeover contact rated 3 A at 250/400 VAC, and a separate auxiliary contact rated 1 A at 24 VDC or 0.1 A at 250 VAC.
The 420-690 VAC rated range covers standard 400 V and 690 V three-phase networks without needing a separate voltage tap. The 3 A contact rating at 250/400 VAC is enough to drive a contactor coil or small pilot load; if you're switching a larger contactor, interpose a slave relay. The separate auxiliary contact (1 A at 24 VDC) is useful for a PLC input or status lamp. Auto-reset is enabled by default — the relay re-energizes once the monitored phase returns within tolerance, which suits unattended restart applications. The 22.5 mm width and snap-on DIN mounting mean it occupies one standard module slot; any mounting position is allowed.