The Apple Watch is a watch in as much as a DVD player or a microwave is a watch. (A DVD player is a machine that people used to play movies at home before Netflix.) That is to say, there is a clock on it—and, okay, fine, you wear it on your wrist—but its raison d'être isn't to tell time.

What, then, is its main purpose? Another way of thinking about this question is: Why would anybody buy this thing? The people who say they won't usually say something like, "But I already have an iPhone." (Plus: It's expensive!)

Already having an iPhone is sort of the point, though. For starters, an Apple Watch doesn't work without one. (They link up via bluetooth.) And thinking about the watch's relationship to its mother-phone is actually a pretty useful way to think about what the Apple Watch might be good for.

A couple months ago, my friend Andrew Phelps, who is a product manager at The New York Times, described to me the usefulness of the Watch in a way I've been unable to stop thinking about since: It is ultimately a device that helps you decide whether to look at your phone.

Which may sound ridiculous. But I don't think it is, actually. Thinking about the Apple Watch as a thing that streamlines interactions with your phone is the key to understanding how useful it could be. As phone screens trend larger, a small watch screen could serve as a preview of what's making your phone buzz in your pocketbook. People already have a habit of checking their phones mindlessly—so much so that the phenomenon of thinking your phone is vibrating when it's not is a thing we have a name for (phantom vibration syndrome). The idea of turning that compulsion into a habit that requires only a glance is appealing, questions of etiquette aside. It's also already natural, skeuomorphically speaking. Or, to put it the way Jack Riley did in a recent Nieman Lab article, “the wristwatch has the advantage of a hundred years of mass market adoption.”

This fits with the idea that the Watch is, it seems, meant to be something you glance at. This is why Apple wants developers to design Watch apps to be used for no more than 10 seconds at a time, according to Bloomberg.

Apple is already marketing the Watch as the most personal product it’s ever made. This makes sense. The Watch is personal because of its physical integration—this is a device that is wrapped around a wearer's wrist, that can recognize the difference between a light tap and a slightly harder one. Then there's the intimacy of the device's tracking capabilities—it can tell you how many steps you take, how well you slept last night, how many times your heart beats in a day.

More significant, though, is that Apple Watch is leading the way in a wearables market that will be increasingly defined by personalized, push-notification-driven interactions with the people and things a wearer chooses to interact with. (The potential for geotargeted advertising could skew that level of choice.)

And this suggests how Apple wants you to see the Watch: a device that saves you the trouble of pulling out your phone. Does that sound like a godsend? Or like it only prevents a small inconvenience? (Or like a non-solution to the king of all first world problems: We can't even be bothered to pick up and look at our miraculous pocket computers anymore.) The success of the product depends on what the average consumer thinks.

So this is what we know about the Watch, before the Apple event Monday. It is a super-small personal computer that Apple hopes will make your interactions easier and more efficient. It will tether you to your phone in a way that could be more streamlined than the existing convenience of a smartphone. Which means—if Apple succeeds—that ultimately, its Watch is a tiny and essential window to the things you care about.