Black tea is grown and processed all over the world in varying geographies and climates. Some of the largest producers of black tea today are Africa, India and Sri Lanka. 

Tea is considered to have originated in China, almost five thousand years ago with legends of green tea linked to the Shen dynasty

As tea culture spread and tea was processed for export to trade around the world, it was discovered that the more oxidized black tea would retain its freshness and flavour better over long journeys than green tea that is minimally oxidized. The length of, or absence of, the oxidation step during the processing of Camelia sinensis (tea) leaves is responsible for the distinctive flavours of black, green oolong and white tea

Types of black tea include Assam, Darjeeling, Ceylon and Kenyan. Even the popular English Breakfast and Earl Grey blends are made from black tea leaves, as are as Lapsang Souchong, Keemun and Yunnan.

Many green teas are still traditionally made by hand using methods that have been handed down from generation to generation. However, more and more teas are now made in mechanised factories. Green teas are totally unoxidised (compared to black teas which are fully oxidised) and so the first stage of the manufacturing process is to kill any enzymes that would otherwise cause oxidation to take place. To de-enzyme them, the freshly plucked leaves are either steamed (to make 'sencha-type teas) or tumbled quickly in a wok or panning machine (to make pan-fired teas) and are then rolled by hand or machine to give the leaf a particular appearance - some teas are twisted, some curved, some rolled into pellets, etc. To remove all but 2-3% of the remaining water, the tea is then dried in hot ovens or over charcoal stoves.

Green Tea varieties include Gunpowder, Chun Mee, Tie Kuan Yin.

White teas traditionally come from China's Fujian province and are made from leaf buds and leaves of the Da Bai (Big White) tea varietal by the simplest process of all teas.  Very young new leaf buds and baby leaves are simply gathered and dried - often in the sun (solar withering).  The best known white teas are Pai Mu Tan (White Peony) which is made using new leaf buds and a few very young leaves, and Yin Zhen (Silver Needles) which is made from just the new leaf buds.

White tea varieties include Pai Mu Tan Imperial and Yin Zhen.

There are a number of subcategories of dark tea of which Pu Erh (Yunnan's famous tea) is the best known. Fu tea is another (Shaanxi Province).

Pu Erh tea is named after Pu Erh city in Yunnan province which was once the main trading centre for teas made in the area.

The official Chinese definition for Pu Erh tea is "Products fermented from green tea of big leaves picked within Yunnan province".  However, even Chinese specialists cannot agree on the true definition but, in general terms, Pu Erh are teas from Yunnan that are aged for up to 50 years in humidity and temperature-controlled conditions to produce teas that have a typically earthy, mature, smooth flavour and aroma.

There are two types of Pu Erh tea made by two different methods of manufacture:  naturally fermented Pu Erh tea (also known as Raw Tea or Sheng Tea) and artificially fermented Puerh tea (also known as Ripe Tea or Shou Tea).

To make naturally fermented Pu Erh tea, fresh leaves from the bush are withered, de-enzymed in a large wok, twisted and rolled by hand, dried in the sun, steamed to soften them and then left loose or compressed into flat cakes or blocks of various shapes.  The tea is then stored in controlled conditions to age and acquire its typically earthy character.

To make artificially fermented Puerh tea, fresh tea leaves are withered, de-enzymed in a large wok, twisted and rolled by hand, dried in the sun and then mixed with a fixed quantity of water, piled, covered with large 'blankets' made from hide and left to ferment.  The tea is stirred at intervals and the whole process takes several weeks.  

When the teas have fermented to a suitable level, they are steamed  in order to render the leaf pliable before being pressed into shape. This can take a number of forms, the most commonly seen being the cake and the Tuocha (a smaller, finger-formed dome). Alternatively, the tea is shaped into balls, or Tuancha. 

The teas are then stored in damp, cool conditions to age.  Naturally fermented Pu Erh teas are left for at least 15 and up to 50 years; artificially fermented Pu Erh teas are aged for only a few weeks or months.  When ready, each cake of Pu Erh tea is wrapped in tissue paper or dried bamboo leaves.

The reason for manufacturing Pu Erh teas by artificial fermentation is to allow the tea producers to make more Puerh in a shorter time.  50 years is a long time to wait for a good Pu Erh so the more modern artificial method was developed to meet a growing demand for these teas.

Flavoured and Scented Teas contain varieties such as Jasmine, Rose Congou and Earl Grey.

According to Will Battle's "World Tea Encylopeadia" - Yellow tea processing is the least know and least practised tea-making style, representing significantly less than 1% of China's total production. The methodology for making yellow tea reputedly lay lost for a centuary before its rediscovery in the 1970s. The yellow tea heartland is Anhui and Hunan with pockets in Sichuan and Henan, and it is seldom if ever witnessed outside of China.

The process is for the most part largely similar to green tea, incorporating solar withering, panning, steaming and sweating, before finally drying.

For more see Will's book here

According to Jane Pettigrew's 'World of Tea' Oolong means "black dragon," and these teas are named for the brown-black, twisted leaves of dark oolongs that often have the appearance of snarling dragons or writhing serpents. Where as green teas undergo no oxidation and black teas undergo a long oxidation, oolongs are partially oxidated (ranging from 10% to almost 80%). There are three styles of oolong: traditional dark oolongs (40-60% oxidised), Bao Zhongs (Puchong) which are lightly oxidised (10-18%) and Jade (Balled) oolongs which are 20-30% oxidised and the leaves are rolled into tight balls.

See more here: Oolong Puchong