To get a sense of how Android Wear works, you could just read through Google's official documentation. But for the more adventurous, why not install the launcher on your Android phone?
The Android Wear launcher is easy to set up, as long as you've enabled installation of apps from unknown sources. Just head to Android Police and grab the APK file from on one of the mirror links at the bottom of the post.
Once installed, you'll see an option to open the “Android Wear” launcher when pressing the home button. A prompt will then ask you to approve Android Wear in the phone's accessibility settings, and after that you'll be ready to check it out.
Keep in mind, however, that the launcher is an extremely rough approximation of Google's smartwatch experience. Google Now and music playback controls did not appear when testing on an HTC One, and voice commands are not yet supported. Unless you have a bunch of items in the phone's notification bar, there's not much to look at.
Still, you can get a general feel for how the interface works, especially if you get a notification from Gmail. Swiping up or down switches between notifications, and every time you tap on a Gmail notification, you'll see a little more of the text. Swiping from left to right dismisses the notification, and swiping from right to left brings up potential actions, such as deleting an e-mail or responding by voice. Think of it as a magnified version of Android's notification bar, with some additional actions and Google Now functionality sprinkled in.
If you really want to go in-depth, Android Police has instructions for installing the Android Wear emulator on a computer, but this is a much lengthier process.
Google announced Android Wear earlier this week, in hopes of getting developers to optimize their existing apps for smartwatch use. The first Android Wear watches from LG and Motorola will arrive in the second quarter and this summer, respectively.