The below PCB belongs to a wireless access point.
Could anyone explain what are the golden-like part of the circuit that is indicated by the red circles(ish)? What material is it? What is the the functionality/use of it?
The left two circles have the same layout on the other side of PCB, and nothing is placed on top. The right circle is just under the wireless chipset.
P.S. I could not come up with a good title as I don't know the proper name or technique that is used on the PCB, please feel free to edit it.