Audio Streaming API's: Wifi vs what?

I've noticed certain radio apps, that some stations required wifi and other开发者_高级运维s did not. What were those other stations possibly using? Are there other methods of streaming audio on iOS?

Apparently, I was not clear in my question before.

I'm asking in terms of API's. Is there an API to interact directly with say, FM radio, on iOS? Is wifi the only way of streaming audio?

Have a look at HTTP Live Streaming:
https://developer.apple.com/library/content/documentation/NetworkingInternet/Conceptual/StreamingMediaGuide/Introduction/Introduction.html