Matcha is some kind of Japanese green tea, in most definitions of the term. It is in fact green tea leaves that are smashed into powder. But not all green tea leaves will be considered Matcha: they are shade-grown for a couple of weeks. The shade-grown aspect is needed for theanine and caffeine producing.
Traditionally the matcha tea focusses on the preparation and serving as a hot tea, but nowadays there are a lot of matcha products available. You can buy the powder and make your own tea but it is also available as coffee or ice cream, etc.