Historically, green tea is one of the first processing methods invented. Consuming raw tea leaves (no processing), and air-drying leaves (white tea) may have been used first. Green tea processing is usually simple: wilt the tea leaves for a few hours, Sha Qing (de-enzyme) using high heat, and then the tea is ready!
There are variations in processing depending on the type of tea and region of production. Green tea's processing maintains the original character of the tea leaf as close as possible, as there is minimal oxidation/ fermentation that occurs.