name for relay that holds state and only consumes power when toggling states
Latching Relay coils tend to be high power and demand short periods of power.
Whereas Non-latching relays can have a high effective current gain of I_contact(max)/I_coil = 1000 to 5000.  Faster power Relays tend to be lower ratios and Latching Relays even lower ratio.

They come in 2 versions;


single coil with bipolar voltage +Set , -Reset, 0V idle these are used all types of "relays" aka ...solenoid, relay , Contactor or transfer switch body.
dual coil with +Set and +Reset being exclusive inputs that are permitted to operate one at a time. Here the common coil end is often metal case grounded. 






There are other ways to make a latching relay too.