This is a wire that connects your sword and lame to the scoring equipment. The Épée wire differs from that used for foil and sabre. You will need one of these if you wish to fence electric.
In foil and sabre there is a choice between the bayonet type socket or the two pin, at the basic level, it does not matter which choice you make just make sure that you have the same socket type on your foil or sabre as the two are incompatible. Most of the club uses the bayonet style socket.