All tea comes from the same plant: the camellia sinensis. From a scientific perspective, herbal teas and beverages that do not derive from this plant are known as "tisanes," including chamomile, peppermint, and ginger "tea." The most common types of tea—green, white, oolong, black/red, and puerh—are formed by taking the same tea leaf and processing it differently post-harvest.
There are two major varieties within the camellia sinensis species—var. sinensis and var. assamica. var sinensis (known as "small leaf") is most commonly found in China, Taiwan and Japan, while var. assamica ("large leaf") is found in India, Southeast Asia, Africa and South America. These varieties diverged during the last Ice Age .
Diving one level deeper, we find cultivars: unique breedings of the plant to cultivate specific properties during propagation. As an example outside of tea, each color of rose represents a specific cultivar. Similarly, food crops are crafted to yield certain quantities, be resistant to disease, and maximize flavor. Here we will spend most of our time, and it should be noted that most countries that grow tea have research institutes dedicated to developing and improving tea cultivars.