What does n/o and n/c mean on a schematic diagram?
RL1 is a relay, a type of electrically-actuated mechanical switch. The swirls are the relay's coil, and the two lines indicate that it's wrapped around a magnetic core.

The thing labelled N/O and N/C is also part of the relay; N/O is "normally open", which means that switch contact is open, or disconnected, when the relay coil is not energized. N/C likewise is "normally closed", which means that switch contact is closed, i.e. connected, when the relay coil is not energized. When a current is flowing through the relay coil, the magnetic field it creates pulls the switch over, opening the NC contact and closing the NO one.

Note that in the context of integrated circuits you may see "NC" used to mean "not connected", but here with it being next to a relay's contacts it's pretty unambiguous.