Green tea is nothing more than the leaves of the camellia sinensis that have been processed a certain way. It is one of the four types of teas ( white , green, oolong , and black ).

Green teas, like white teas, are closer to tasting like fresh leaves or grass than the black or oolong. They are also lower in caffeine and have higher antioxidant properties.
 
The Processing of Green Tea

The processing of green tea is similar to that of white tea in that it does not oxidize. After the leaves are plucked, they are (sometimes) laid out to wither for about 8 to 24 hours. This lets most of the water evaporate. http://www.essaygobuy.com/

Then, in order to neutralize the enzymes thus preventing oxidation, the leaves are steamed or pan fried. Next the leaves are rolled up in various ways and tightness.

After that, a final drying takes place. Since no oxidation took place, the tea has more of a green appearance. From there, it goes off to be sorted, graded, and packaged.