Green tea is made from the leaves from Camellia sinensis that have undergone minimal oxidation during processing.
green tea n : tea leaves that have been steamed and dried without fermenting
Matcha, also maccha, refers to finely milled or fine powder green tea. It is considered to have more health benefits than traditional steeped green tea due to how it's cultivated and processed. It also has more caffeine.
Additional data for matcha-green-tea may be on the way.