> It's neither like iMessage
It will provide a similar experience, a default messaging client that gracefully enhances the SMS experience we're used to.
> nor specifically for Android
It's a standard, but considering Android is the biggest mobile operating system and the second biggest has it's own version of this, and the protocol is being pushed by the Android's creators, it's fair to say this is "for Android", at least at first.
> It's not, it's (like SMS) carrier infrastructure. Chat is just an RCS client app, RCS is the SMS replacement technology.
It's possible that Google would provide services to support it, the same way Apple provides the service for push notifications.