What's The Difference Between Green Tea And Black Tea?

They are both made from the leaves of the same species of plant (Camellia sinensis) , but processed in different ways.  

Tea leaves are hand-plucked.  Green tea leaves are immediately steamed or baked after harvest, and then rolled and dried.  They retain a green colour.

Black tea is also hand plucked, but then it is left to wither and oxidise (a process called fermentation among producers).  Then the leaves are rolled (crushed) and left to wither/oxidise some more.  After that they are dried and sorted as for green tea.

Other traditional varieties of tea made from Camellia sinensis are oolong tea (partially fermented, so part way between green and black tea) and white tea, which is fermented but made from the buds and very young leaves of the plants.

There are small differences in the possible health effects from drinking the different types of tea.  All are rich in beneficial flavinoids, all pose health risks at high levels of consumption.

Ideally nearly-boiling water should be poured over ordinary black tea, but green tea tastes better when infused with water 80-85 deg. C.

Green tea has more of a citrus-like flavor while black tea tastes more bitter and what the brits drink during "teatime."