Question about Microsoft Xbox One Wireless Adapter for Windows

You could connect up to 8 controllers, up to 4 chat headsets and 2 stereo headsets to an Xbox Wireless Adapter.
Why the 2 adapters?

And does it also work on a PC? Does an "old" adapter also work on an old and new controller? The new one has USB-C and the old one micro-b? So the old adapter can read the new generation?
Or can the new adapter then recognise the old generation?

thank you (: that's exactly what i wanted to know! i would take off my hat but i don't wear one