What does the fuse do in a three-pin plug?

The 3 pin plug is used to connect (and eventually disconnect) various devices requiring an AC power supply to and from the main power supply.

As the name suggests, the 3 pin plug consists of three pins :-

1. Longer one, usually on the top for most standard plugs : is the earth [ E ]
2. Left pin (Usually) : is the Line connection [ L ]
3. Right pin (Usually) : is neutral [ N ]

Next to the pins, on the plug, the three pins and their respective function is given by E, L and N.