In addition to a touch-screen interface that lets you tap and swipe your way through the system, the Apple Watch also offers several new means of interaction. A Digital Crown knob on the right edge acts like a home button. You can press this to return to the main screen, or turn it to zoom or scroll through options in the interface.
Next to the Digital Crown is a dedicated button that pulls up the Friends communication tool. This lets you contact a select list of people via your Apple Watch