What we've been calling iRadio is officially iTunes Radio. Two things define it:
#1. It's built right into the Music app so it's basically a service.
#2. It's free with ads and if you're subscribed to iTunes Match, there are no ads.
Let's first talk about the Music app in iOS 7.
It has been completely redesigned but what's impressive is unification. Your purchased music shows up, so do your TV shows and movies. The integration allows for a unified experience instead of having to confuse yourself between iTunes and iDevice.
Itunes Radio is a free service that runs with ads. No details are clear about how the ads will be delivered but if existing services are anything to by, you should hear in-stream ads.
For those subscribed to iTunes Match, you will be getting ad-free iTunes Radio.
An interesting thing noted at the WWDC 2013 was that iTunes Radio was the first time that featured Led Zeppelin. iTunes Radio, by the looks of it, seems like the Pandora-competitor. With 300 million iTunes users, I guess Apple will be taking off well even if a few users decided to give it a try. Knowing Apple and its band of fans, iTunes Radio should be a successful experiment.
iTunes Radio, while letting you listen to ad/ad-free streams of music from various stations also allows you to share or create a new playlist out of stations. Much like the Podcasts app, we guess. You can also download individual tracks if you wish to. These will get directly under the Purchased Music section of your Music app.