it's green tea
Green tea enthusiasts believe it to be useful for:
Stopping certain neurodegenerative diseases such as Alzheimer's
Treating multiple sclerosis
Preventing the degradation of cell membranes by neutralizing the spread of free radicals (which occurs during the process of oxidation). 
Increases fat oxidation (helps the body use fat as an energy source) and raises metabolism. 
Lowering LDL cholesterol (in high doses in lab tests)
Preventing lowered T-Cells due to HIV - In lab tests, EGCG, found in green tea, was found to prevent HIV from attacking T-Cells. However, it is not known if this has any effect on humans yet. 
The U.S. Food and Drug Administration (FDA) has rejected claims of health benefits for green tea. 
"There is no credible scientific evidence that drinking green tea reduces the risk of heart disease."
"FDA concludes there is no credible evidence to support qualified health claims for green tea or green tea extract and a reduction of a number of risk factors associated with CVD" (cardiovascular disease)."
The FDA has said that green tea likely does not reduce breast, prostate, or any other type of cancer risk.