MacRumors writer Juli Clover explains,
Theater Mode can be accessed by swiping up on the watch face to bring up the Control Center. It’s just below the option for silencing the Apple Watch and features an icon with two theater masks. When Theater Mode is turned on, it prevents the Apple Watch from making noise and it keeps the screen dark even when the wrist is raised. Notifications still come through, however, and are delivered via haptic feedback. The Apple Watch’s screen can be activated with a tap or through a press on the Digital Crown.
In addition to Theater Mode, watchOS 3.2 contains SiriKit which will expand Siri’s actions to sending messages, making payment, booking rides, and other actions within individual apps. WatchOS 3.2 is expected to arrive around March.