It's actually from a fungi family and is claimed as "one of the most precious and rare wild medicinal plants in China".
It's actual name is Ling Zhi, and it's supposed to:
Provide more energy and vigor, less fatigue and increase brain power
Rejuvenate and make you feel young and alert
Strengthen the organs for waste elimination and detoxification
Strengthen the body's immune system
Promote a good night's sleep
Personally, I havn't tried it yet.
But it's on my list of things I need to get (whenever I can. ^^; )