NFC. If i recall the inside of my battery cover, you're talking about the NFC stuff. I have a case on which im not going to take off (it's a PITA) but I'll bet thats what you're referring too. Looks like little metal connectors? Gold in color? Thats for NFC
Those connectors are for external radio frequency antennas, commonly used in repair and testing. I'm not sure which antenna does what, but those are going to be used for wireless data, calling, gps, etc.