You can project your Chromebook's screen on an external monitor or via a projector, connect the device to your Chromebook. Once connected, the device will be automatically detected and your screen will be projected, using the best possible resolution.
If you've connected an external monitor, the screen will only appear on the external monitor. If you've connected a projector, the screen will be displayed on both your Chromebook and via the projector.
Note: If your Chromebook isn't projecting, you can try pressing Ctrl and refresh to manually reconfigure the monitor. If no external device is detected, the screen won't project.
For more information about your screen display settings, visit Google's Screen display settings page.