NO vs NC

[Ger21]

No.
NO means that the circuit is open, and no electricity is flowing through it.
NC means the circuit is closed (as in fully connected), and electricity is flowing through it.

Say you have a normally open limit switch. Elctricity only flows through the circuit when the switch is triggered, closing the circuit. If the wire were to break, you'd never know it.
That's why limit switches are normally set up as NC. So that a broken wire will open the circuit, and trigger the limit input.

[m_c]

NO = Normally Open aka open circuit
NC = Normally Closed aka circuit complete

NO/NC is always described in the non actuated or unpowered state.

As Ger has explained, for anything safety critical, you would normally use a NC circuit.