240V Wireless 433Mhz Relay Wiring
From looking at the circuit board in your photographs:

NC - Normally connected. This be continuous with COM when the relay is not activated

ON - What it says, on. This should be continuous with COM when the relay is activated

N - Neutral leg from the mains voltage

220 V - This is marking an unused terminal on this device, but indicates that the line voltage expected is 220 VAC. 

L - Line power, or the hot from the mains.

If you can find a spec. sheet on this device it'd be much simpler to figure out how it is supposed to work.

The electronics on this device obviously need low voltage DC power. Given the absence of a transformer of any kind, DC power supply is probably supplied to the circuit by a combination of capacitive &amp; resistive current limiting from the 220 VAC line. This feeds a rectifier (possibly half wave), a capacitor, and probably a cheap regulator somewhere.

The resistor on the corner and the large brown capacitor beside it are probably fed from the 220 V terminal and make up the current limiting circuit.