Latching relays provide a unique feature that can be used in any basic relay form, SPST, SPDT, or DPDT. Most relays and contactors are considered “fail safe.”
Fail safe relays require coil power applied continuously to make sure the relay is switched.
Once coil power is removed the moveable contact in a fail safe relay returns to its default position.

Latching relays require a momentary coil pulse to change the position of the moveable. Continuous coil power is not required to keep the relay in a particular switched state.
When the application circuit needs to switch a latching relay it sends a pulse to the coil to change the moveable contact position. 
Complete specifications can be found by downloading the PDF datasheet below.