Green tea is an excellent beverage. Matcha is green tea, optimised.
Green tea is normally consumed as an infusion, produced from tea leaves which are discarded before the tea is consumed. Such green tea infusions are a perfectly rational choice.
A 2007 study strongly suggests that green tea catechins (a form of antioxidant) may help to counter cardiovascular disease risks by interfering with our digestion of fat and cholesterol. Later, a 2010 study confirmed that green tea is one of the best sources of antioxidants available to us.
So how does matcha work? Well, matcha is green tea, so it packs all these benefits too.
The difference is that matcha is not an infusion. Rather, it is a suspension, in which the whole green tea leaf - stone-milled to a fine, bright green powder - is consumed along with the water or milk product in which it is mixed.