This is not only a simple switch board. Of course it is an electric switch board but with some additional feature. One of its 5 pin top (left side) works normally when the connected (adjacent) switch is on but when the switch is off and any electric appliance/device or load is connected, the green LED indicates its continuity.

Step 1:

In this picture left side's 5 pin outlet function is some special. When the connected switch is off and any electric appliance/device or load is connected, the green LED (Tester LED) indicates the continuity of the connected device.

Step 2:

If the LED (green) glows then the connected device is OK! and if it does not glow, it means the circuit is broken. This is useful you can make one by watching this video.