When we talk about “tea” we always refer to the processed leaves of camellia sinensis. In English, we have “herbal tea” or “herbal infusion” or even the out-of-date and out of use “tisane” to refer to any kind of herbal infusion that is not made from the leaves of Camellia sinensis. However, it is most common say “peppermint tea” e.g. instead of “peppermint infusion” or even “peppermint tisane”, and that’s how “tea” has entered our everyday language with the meaning of “a brew of some plant material”. You find more information on herbal infusions under Herbal Infusions / Other.
Of course there are many varietals united under the genetic umbrella of the camellia sinensis species, just as there are many varietals of grapes like Cabernet Sauvignon, Chardonnay, Merlot, Pinot noir, Syrah and many others under the term “grape”. All varietals belong to the family of camellia sinensis, the tea plant, though. An overview over the different sub-varieties of the tea plant can be found under Varietals of the Tea Plant.
Camellia sinensis develops, in its wild state, into a tree several meters high. It requires a subtropical climate and can get hundreds of years old. Such very old trees are still being harvested and their leaves processed into teas of very high quality. The province Yunnan has tea trees that are over 1000 years old, and they are still harvested. In the common cultivated form of the plant, however, the tea tree is cut back into a bush of approximately one meter height. Plucking usually occurs by hand, but there are some exceptions such as in Japan, in some parts of Taiwan, and on big plantations. But also in China, machines are increasingly used for the harvesting of teas of simple quality, since the pluckers' wages rise from year to year and there are ever less of them at work. The plucking rule for good teas is still “two leaves and a bud”, i.e. the uppermost leaf bud and the two leaves underneath. Yet still, there are a series of exceptions to this rule, too.
After the plucking the leaves are processed into different kinds of tea. It is the type of processing that defines the type of tea obtained. The leaves of the tea plant can be processed into white, yellow, green, Oolong, black or postfermented tea. You will find further information on this topic under Types of Tea Processing. Hence, from the Camellia sinensis plant only these six kinds of tea are made. Every tea can be tracked back to one of these six kinds of processing. The infinite diversity in the offer of teas comes from the chosen varietal of the tea plant, geographical and climatic differences, and of course from the steering influence of the human hand, the artistic imprint of the tea master’s handwriting who is guiding the process. In the terminology of wine, there is this wonderful concept of “Terroir”, which perfectly includes all of these aspects and influences.
As the tea leaves themselves are a raw product, there are differences in how they are brewed. These are coined by different customs and conventions, i.e. culturally different ways of preparing the tea. There is the famous English tea e.g., even though the tea plant is not cultivated in England (with exception of one single tea garden in Cornwall). The term “English Tea” hence refers here to the way it is produced, adapted to the peoples’ taste and the country’s quality of water, and how it is served, rather than to the geographical provenance. Then there is the Indian tea, which is grown and produced in India, like Assam, Darjeeling or Nilgiri. Here we do have the link between provenance and name. At the same time, however, there is the tea served the Indian way as “Chai”: black tea with spices and milk. Similarly, the North African “Thé à la Menthe” (lit. tea of/with mint) does not refer to tea leaves cultivated in North Africa nor to a pure peppermint infusion, but rather to a many centuries old tradition of drinking tea, a combination of China (and its green tea) and North Africa (with its mint).