You aren't missing anything Jim! there seems to be just a communication gap here. No worries, here's the clarification:
the "coins" as most people call them, are the MOBILE ONLY quasi currency that are good for next to nothing other than PvP matches/clashes. it looks, literally, like a pile of silver coins.
the "credits", as most people call them, are the ones with actual $$$ value and are cross platform. they appear on mobile next to a gold circle that I can see someone calling a "coin" due to the shape of the graphic. I play 99% on mobile myself, so I am not totally sure how the CREDITS are displayed on the web app client.
@Lucky it is just a terminology thing here. easy enough to happen and remedy. moving forward, just call the "gold coins" CREDITS and that will clear up any confusion on the forums. cheers y'all!