anyone know what it is for? for ipad air 2 cellular?

Thanks for replying if u go wire things all the way there is antenna things at corner link together can u see? It looks same as ipad 5 and 6

You are right. Upon closer inspection I have realized what you mean.

The damaged IPEX cable can be replaced for cheap if you know how to solder, but the EMI resistance will be reduced and you will probably suffer more interference. If that bothers you, you can probably source a replacement from an online store or a broken donor iPad.

I am not sure what the broken antenna might do, but I believe it is responsible for 4G LTE MIMO (Multiple In, Multiple Out) for higher speeds. It is not vital for basic functioning, but it may significantly damage your network speeds.