There are two categories of teas, camellia teas and herbal teas. Camellia is the plant that virtually all teas, of which there are four main categories, originate from. The types are: black, oolong, green and white. The main difference is how much oxygen the teas are allowed to absorb during the drying process, black teas receiving the most and white teas receiving the least, with oolong and green in between.
Black tea is the most popular variety in countries like England and the US, while green tea, with its rather grassy flavors, remains the most popular in other tea drinking countries, like China. Oolong is a semi-oxidized tea that can resemble either green or black. White teas are the least processed teas, made from the very highest quality leaves. They have a very clean flavor and their health benefits are currently being explored as they gain popularity.
Herbal teas, also called tisanes, are not actually teas. They are tea-like infusions of non-tea plants or flowers. Chamomile is probably the most famous of these teas, made from a dried herb. Rooibos, another popular herbal tea, is made from a type of bark. Herbal drinks often boast of a variety of health benefits, the most common of which being their calming or relaxing effect, since they do not contain caffeine.
Flavored teas are teas that are flavored with the essential oils of the desired flavor, like citrus, or have spices added in with the leaves.