WebRTC is just a protocol for applications. So you'll need to have Hangouts or Skype or whatever client using WebRTC open, and then it should work when someone calls you through them, on the web.
Take Facebook Chat for example or whatever they are calling that integration with a Java Skype plugin. Instead of using that Java plugin, it could use WebRTC in the future, and it won't even need Skype. It could just work with Facebook users, which is something Facebook might want anyway, or at least until Skype uses WebRTC, too.
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WebRTC is just a protocol for applications. So you'll need to have Hangouts or Skype or whatever client using WebRTC open, and then it should work when someone calls you through them, on the web.
Take Facebook Chat for example or whatever they are calling that integration with a Java Skype plugin. Instead of using that Java plugin, it could use WebRTC in the future, and it won't even need Skype. It could just work with Facebook users, which is something Facebook might want anyway, or at least until Skype uses WebRTC, too.