This is a confusing one, so bear with us! Oolong tea is commonly referred to as semi-oxidized tea or wu-long tea. But tea is kind of like wine: it all comes from the same Camellia Sinensis plant, and the categories of tea–black, green, oolong, white–are differentiated by their processing methods.
The main factor in processing is oxidation. It's the same chemical process that makes your apples and avocados go brown, and it's also what defines the big categories of tea.
Green tea is 0% oxidized and black tea is 100% oxidized. Oolong tea is partially oxidized, which covers everything in between green and black teas. It's a lot! But it's also the reason oolongs cover such a wide range of flavor variations.
Lightly oxidized oolongs tend to be similar to green tea, more vegetal and grassy but with hints of white flowers. Heavier oxidized oolongs tend to carry richer floral notes with maltier aroma and more similar to black teas.
We wrote a more in-depth blog post on the subject here if you are interested in reading further.
