Oolong is a semi-oxidized family of teas that can range in oxidation from 10% - 70%. This category of teas spans a wide range of flavors, aromas, and hues, and is often thought of as the bridge between green and black teas.
Oolongs tend to have a less pronounced tannin, making them less astringent than either green or black teas, due to their only partial oxidation. The lighter oxidized oolongs (below ~45% oxidation) are often referred to as green oolongs and have flavor profiles and liquor colors similar to green teas. Lightly oxidized oolongs are delicate in character and usually have flavors and aromas of white flowers, fruits, and greens. Black oolongs, or dark oolongs (greater than 50% oxidation), resemble black teas in color and flavor profiles. You may notice flavors of dried fruit, spice, malt, or minerals in your dark oolongs.