What's included

Source: https://www.vive.com/uk/support/focus3/

• The Headset

• Two controllers 

• 2 lanyards

• AC Adapter 

• Splitter Cable for charging 

• Lens Cleaning Cloth 

• Documentation

Charging the Headset

You can charge the headset with the AC adapter.

Charge the headset by connecting the AC adapter to a power outlet, and then connecting it to the headset. Charging the headset while in use is not recommended.

source: https://www.vive.com/uk/support/focus3/category_howto/charging-the-headset.html

Useful links:

HTC Vive Focus 3 unboxing 

HTC Vive Focus 3 - About the headset and the controllers