Green tea is rich in antioxidant called catechins, especially epigallocatechin 3 gallate (EGCG), which scavenge free radicals. Free radicals can damage DNA and contribute to blood clots, cancer and atherosclerosis.
It is considered beneficial for some types of cancers, heart disease mainly due to atherosclerosis, weight reduction and general immunity. It is very refreshing also.
Still there is a question how much green tea one need to drink to reap its health benefits.
But still one can enjoy it often.