My understanding is there are several different kinds, just like black or herbal tea.
In general, green tea is just black tea that hasn't been "roasted", and therefore has fewer cacinogens. It still has caffiene. It's like herbal tea in that sense. Some green tea is just barely grass that's brewed the same as regular tea. It's good for digestion.
There are some green teas, Chinese mostly, that aren't made from the same leaves as black teas. Some of the pearled stuff. It's very potent and fragrant. And best purchased from a tea merchant knowledgable about such things. These types of teas are very high quality and can actually be reused several times before their potency is diluted. They still may have caffiene.
Tea is pretty complicated and I don't have any pointers to information. There was a Chinese tea shop downtown where we lived and one day we went in and talked tea with the man who worked there. We felt a little self conscious because we didn't know anything, but he was very helpful and talked at length about the different types of teas and what to look out for.
The other stuff I figured out from other sources.
Sorry nothing specific.