In its simple form, a micro switch have 3 terminals, Common(COM), Normally Open(NO) and Normally closed(NC).
Common(COM)- Always has power(electricity) so don’t confuse with ground, we don’t have ground on switches.
Normally closed(NC)- When the micro switch is on its resting position NC is connected to the common
Normally open(NO)-When the micro switch is pressed, the common connect to the NO (normally open)
The inside of a micro switch