These are high quality Single Pole - Double Throw (SPDT) sealed relays. Use them to switch high voltage, and/or high current devices.
This relay’s coil is rated up to 12V, with a minimum switching voltage of 5V. The contacts are rated up to 5A (@250VAC, 30VDC).
(Ever wonder why switches are always rated for way more AC voltage than DC voltage? It's because AC crosses 0V 120 times a second, which means the arc is quenched much more easily. DC voltage is constant, which means it sustains much longer arcs for the same RMS voltage.)
Note: In the Datasheet below there is a pin layout listed as “Bottom View.” Be aware, this pin layout is actually the top-down view NOT bottom-up.