Black tea leaves are rolled, slightly bruised and ‘oxidized’ leaves which makes them darker in color resulting in stronger flavor than other teas.
Oolong tea leaves are oxidized but the process is halted before the leaves become fully oxidised leaving it with a slightly bold and natural flavor.
Green tea leaves are fired or steamed to ensure they retain their green colour and natural aroma. Since they are not oxidized, it retains higher levels of antioxidants, tannins, vitamins and minerals and has a lower caffeine level than black tea.
White tea leaves can be only picked when the tea plant forms new buds. The buds are just picked and dried and are the highest in antioxidants.