Most time, PUSH BUTTON SWITCH would be classified according to the contact configuration
The contacts could be 1NO,1NC,1NO1NC, 2NO2NC, 2NO,2NC,3NO3NC. etc.
NO Contact means that the contact would be disconnected when power is off. When the power is on, it would be connected. When a momentary switch is not actuated, it’s in a “normal” state.
NC Contact means that two contacts would be connected when power is off. On the contrary, it would be disconnected when power is on.
Here attached NO,NC Symbol as the explanation.
1. SPST--NO (X type) and NC (Y type)
2. SPDT--1NO1NC Contact (C Type )
3. DPDT-2NO2NC Contact, would be two SPDT switches controlled by a single mechanism