Oticon streamer - how does it transmit?


I'm trying to understand the difference between using something like the Oticon streamer and using a neck loop.  

I understand that the streamer will pick up bluetooth from my phone so I don't need the streamer physically plugged in to it.  But what I don't understand is how the streamer transmits sound to my hearing aids.   The internet suggests that it won't work with the aids on telecoil, so if it isn't using a loop system, how does it work?  

Can anyone enlighten me?