To clarify the difference between normally open and closed, please consider the chart shown here. Normal open switches means the circuit is open in the released position. Then when actuated, the circuit is closed. Normally closed, on the other hand, is the opposite. There are certain advantages to having a normally closed type. First is reliability and stability. It is easy to know if the switch is functioning because the signal is passing through under the normal condition. There is also a decrease in power consumption because power is only consumed when the circuit is opened.