Oolong teas are a semi-fermented tea, half-way between an unfermented Green tea and a fermented Black tea. Taiwan or Formosa as it was once known, is an Island famous for it's Oolong teas although they are produced all over the tea growing world.
An Oolong is generally considered an Afternoon tea and would be drunk without milk. Possibly a slice of citrus or a small amount of honey if one has a sweet tooth.
You would generally prepare an Oolong tea by heating fresh water to 90 °C and steep for between two and three minutes.
Proper China Cups are called for when taking this beverage and either a small slice of cake or possibly cucumber sandwiches, crusts removed (obviously)