Darjeeling Oolong is an amazingly diverse class of tea. It can provide flavours as fresh and vibrant as a green tea or as bold and invigorating as a black tea. Its differences are largely dependent on the length of time the oolong is oxidised.
Oolong is known as a "semi-oxidised" tea. The process can be allowed to progress anywhere from 10-80% (although most oolongs are 25-80% oxidised).