White tea is made from the tender buds of the tea plant Camelia sinensis. Freshly dried tea leaves often contain one third methylxanthines like catechins. These are the anti oxidants which make teas so healthy, preventing cancer and skin damage. White tea is unoxidized and has particularly potent anti oxidant properties.
Green tea is very similar to white tea except that it is made from older leaves. It is very high in catechins, as the leaves have not been allowed to oxidize. Green tea can rejuvenate skin, and protects the body against free radicals. It is a more powerful anti oxidant that vitamin A.
Black tea is "fermented" green tea. It is not really fermented, it is just that the fresh leaves contain enzymes which oxidize the catechin. There are three stages of oxidation. In an Oolong, the oxidation is partial, so it is a half green and half black tea. a pu'er type of tea has been oxidized more than usual.
