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The bottom 3 pins are for the user to utilise. When the mic. picks up a loud noise the relay pulls in and the contacts at the bottom change over. At present they are wired to make a mains powered bulb come on.
If you do not understand this sort of thing you should not be thinking about wiring up a mains powered piece of equipment, you are likely to injure your self.
The three output pins are the NC, NO and common.
When the coil is not powered then the common is connected to NC (Normally Closed) , when the coin is powered then the common connects to NO (Normally Open).
In your schematic the lamp is connected to NO, if you want you can connect a second lamp in the NC and then one of the two lamps will be on depending on the relay state.
Also you can use only NC instead of NO if you want the lamp to be on by default and turn off the first time you clap.