Oolong tea is a semi-oxidized tea. The level of oxidation may vary from 8 to 80 percent. Lighter oxidized oolong teas resemble green tea, and heavily oxidized oolongs have the taste and look of black tea.
The manufacturing process of oolong tea is complex and contains a lot of individual steps, that other types of teas don’t undergo. Oolong originated in China and has spread to Taiwan.