What is this connection responsible for?

Hello!

Some time ago my macbook air got soaked in the rain. I dried it, properly cleaned it, everything was working (except battery and trackpad is a bit wonky). The only problem was that during the cleaning I saw that the connection that I circled in the photo, was completely rotten, disintegrated, the chip to which the cable connects fell of from the corpus. What is this cable responsible for? I could not find any info on the net.

Also, at the same time, my keyboard started to disconnect from time to time. It was not working for a week ,then started working again for few days, now stopped working again. Could it be because of the swelled battery? Or this implies that there is another connection which is starting to break down?

Thank you very much for your answers!