The process to turn the Camelia Sinensis plant leaves from green to black is called Oxidation. This same process helps turn the soft downy buds from white to gold. Teas which have these golden buds have the name "Golden". Monkey refers to an old tale where tea sellers would indicate a tea was "Monkey Picked" if it was rarer than most. Thus, we have Golden Monkey from Adagio Teas.
Yellow Tea is very rare. Manufactured only in China as the processes to make it are kept very close to the vest. Even in China, yellow tea has a high level of prize and mystique. I found some from Harney & Sons, and wasn't disappointed!