Yesterday we focused on the "what" of Microsoft Kin, explaining the ins and outs of the new devices designed to appeal to a generation of hyper-social mobile phone users. But given that Microsoft just revamped its broader mobile phone initiative with Windows Phone 7, the bigger question is why the company felt it necessary, with the Kin, to launch what amounts to a completely separate product line.

In interviews since the Kin unveiling, Microsoft has been fielding scores of questions on that topic, giving responses that shed light on its thinking, even if they leave room for debate about its reasoning. After quizzing a Microsoft product management director, Wilson Rothman of Gizmodo came away with this conclusion.

"Essentially, Microsoft is consciously aiming two totally separate products at two totally separate buyers, ones who aren't supposed to cross paths," Rothman writes. "And if they do meet up, it will be a few years down the road, when the two phones might have more in common than they do now."

Robbie Bach, president of Microsoft's Entertainment & Devices Division, went into more detail in an interview with Cris Valerio of Bloomberg News, explaining why Microsoft decided to get involved in the end-to-end design and marketing of this particular line of phone:

The whole idea of this, if you look at our broad Windows Phone strategy, we have Windows Phone 7, which is sort of our multipurpose entry for the broad marketplace, but then we decided, we said, look, there's a segment here that we can really go after deeply. They're very passionate about their technology, they're very passionate about their phone, and once you decide to go deep you can't go partway. You can't say, oh, we'll do the software and then we'll hand it off to somebody else. You have to really be involved in the whole process.

First of all, it's a growing segment. It's an evolution. It's an audience that starts at 14 and 15, goes to 30, and those people are going to grow up, so you're trying to reach people early on in their engagement with technology. Second thing is it's an audience that is very passionate about technology and very facile with it. So they expect things to work, they know how things work, they expect things to be multi-screen. That's really where our strategy is. So it really made sense for us to drill in on that.

Finally there's the more basic question: Kin? What kind of name is that?

"It means family, it means togetherness," said Microsoft's John Starkweather, when I asked that question during a press briefing yesterday. "These are my words here, but kin is the type of family or friends that you would shed blood for, that you would do anything for, and that's the things that are more important to you. That's the essence that we were trying to capture."

There, does it all make sense now?

Previously: Microsoft Kin hands-on video and first take