I'd like to be really precise, madam, about the “you” and the “it” in your sentences because I think you used them correctly, but there is a subtle distinction there. “It”—your phone—does know that. Your phone is collecting based on sensor data and behavioural patterns and tries to infer where your home is—and that is your iPhone. “You”, being Apple, does not know this information, or at least not via that process. If you leave a billing address with us for purchases or something, that's different, but the information that your iPhone is becoming intelligent about remains on your phone and is not known by Apple.
When you ask about how much of it is collected, well, it's collected by the phone. It's collected under our “frequent locations” feature. Users can go and browse and remove those inside the device, but the collection is just for the device. It's not actually collected by Apple.
As for the purposes to which it can be put, over our versions of the operating system we try to use that information to provide good local experiences on the device, such as the time-to-leave notifications or notifications of traffic incidents on your route home; but that isn't going to extend to purposes to which Apple, the corporate entity, could put that data, because that data is never in our possession.