Green teas are lightly processed, lightly oxidised teas - while the category covers a wide range of tastes and processing methods, generally speaking green teas are dried but not roasted or oxidised and retain their original bright green colour, especially when brewed.
Green Chinese teas are non-fermented, non-oxidised, fresh tea leaves. They are wilted and dried in a similar way to other teas, but unlike other teas do not undergo any form of oxidisation or roasting. As a result, they have an exceptionally fresh and pure taste, and a beautiful light green colour.
Good Chinese green teas command high prices in China and across the world. Because they are fresh and unaltered by any excessive processing, a good green tea represents as close as it's possible to the original taste of tea. For example, genuine bi luo chun and long jing teas often sell for as much as £400 per half kilo in China, which tells you a lot about their taste and demand!
Green teas are light in caffeine and high in anti-oxidants, which is why many people believe them to be the most beneficial for health. They're most often grown in Zhejiang, Anhui and Jiangxi provinces, and often have quite a short shelf-life (3-6 months unrefridgerated).