DPDT : Double Pole Double Throw

DPST : Double Pole Single Throw

SPDT , SPST : Home Work

If you connect a battery to a circuit via a DPDT switch, you can isolate both + and - poles.

If you connect a battery to a circuit via a SPDT switch, you can isolate one pole, maybe the +ve and leave the -ve pole permanently connected.

Ans so it goes. Maybe there are numerous other ways to use them.

Bye

Raghu