Who know's what this cable is called and where to get one from?

Hi,

Whilst replacing the back housing of my iphone 5, I noticed that one of the contacts at the end of the cable was still attached to the main board, and had come away from the cable itself.

Does anyone know what this connection does (the square pad that the pry tool is next to)? I've tested the main bits of the phone and can't notice anything that isn't working even though the cable isn't connected to the connector any more.

https://d3nevzfk7ii3be.cloudfront.net/ig...

Also, do you know the name of the cable, as I want to buy a replacement one.