Green tea tea that has not been oxidized. After the withering process, tea producers will use heat to kill the enzyme that produces oxidase. This is the enzyme that promotes oxidation.
There are multiple different ways a tea producer can kill the oxidase within the plant. A lot of them are country specific. Tea producers in Japan use steam, most of the time and in some small cases, a combination of the two. Tea producers in China and Taiwan use ovens and woks. At least one tea in China is heated with steam instead of a wok or oven.