I'm pretty sure that's a ground plane intended to be affixed to the underside of the supplied antenna to improve its performance. One of the clues is the presence of the adhesive; another is the size of the mesh. A nice touch for that to be included in the package.
Hope this solves the "Mystery of the Thing."
My module has an adhesive "thing" on the feedline about half way down. This "thing" is fine metal mesh and is connected to the shield of the feedline. It seems to be common on the tiny ceramic antennas on eBay but many also don't have it.