I didn't know what it was either until a friend recommended it
It's oolong green tea, premium because it's produced in Taiwan's highest altitude tea production area, and it's becoming rarer and rarer nowadays (or at least so was I told). The appearance of the leaves is deep green, and tightly rolled in small pellets but will open nicely after you infuse it.
The taste...? Hmm... How can I describe this and do the tea justice?
Autumn came to mind when I smell it. It has this earthy but also fruity aroma. Like a forest in the fall. The flavor is refreshing, crisp but also balanced by natural sweetness, and has a flowery finish as well as a creamy aftertaste. I don't know if that makes sense
I found a video, maybe interesting for you to watch: