What are the differences in green, white, oolong and black tea?

Green, white, black and oolong teas, “cha”, all are made from the tea plant Camellia sinensis. Black tea leaves are oxidized during drying. This turns the leaves black and gives black tea a strong, robust flavor with a high caffeine content. Oolong tea is semi-oxidized and falls between green tea and black tea in flavor and caffeine content. Oolong has a smooth, mellow and fragrant flavor. Green tea is heat treated and dried immediately after harvest. This stops the oxidation process and keeps the leaves green. Green tea has a lower caffeine content and a mild and aromatic taste. White tea is the least processed. The young tea buds and leaves are picked, withered and air dried, then heat treated to remove more moisture. This results in the unique, subtle, fragrant, complex, slightly nutty flavor of white tea. Research varies on the caffeine content of white tea. Some show it to be very low and others higher.