What’s the difference between Normally Closed thermal switch and normally open thermal switch?

Normally closed thermal switch means that the contacts of thermal switch normally remain closed. When temperature increases to the set value, the contacts would open and cut the circuit OFF.

Normally open thermal switch means that the contacts of thermal switch normally remain open. When temperature rises, the contacts would close and connect the circuit ON.

We now have several models that both Normally Open and Normally Close type are optional, like 17AME, TS01, KW, KSD301, 3MPE, and so on.