IPTV stands for internet protocol television. You can buy a subscription service for your device that gives you basically any tv channel you could want.
Usually a lot better quality and more reliable than your average football stream, football being the main reason I buy it. Not entirely legal so there is a chance they get closed down and you never hear from the supplier again.
I got mine of ebay and the guy has actually got back to me. Said the servers were down for a bit but if I restarted my firestick it should be fine. And it was.