While the service hasn't been officially announced yet (there's a 10 AM PT/1 PM ET talk scheduled for June 9 at WWDC), Business Chat is touted as a way for consumers to interact with businesses and make purchases on the iPhone, iPad and Apple Watch. It will be integrated into some of Apple's native apps, including Safari, Maps, Siri and Spotlight. While the actual chatting will presumably happen in iMessage, the service will originate within these apps.
It's not surprising Apple is making the foray into facilitating communication between businesses and consumers; after all, it's in their interest to keep as many people within their own ecosystem as possible. The more you can do with an app, especially one that integrates features such as Apple Pay, the more likely you are to stick with it.
There's a growing trend toward instant customer service communication. Facebook has been improving Messenger for businesses, and Twitter has been working on customer service features for years. As we move more towards instant customer service through private messaging (rather than phone or email), it will be interesting to see how these services develop new tools to enhance communication. One thing is for sure though: the way we interact with businesses is quickly changing, and hopefully for the better.