Tea has almost no carbohydrates, fat, or protein. It has a refreshing, slightly bitter and astringent taste. There are four basic types of true tea: black tea, oolong tea, green tea, and white tea which are made from the same tea leaf which comes from the Camellia sinensis plant. These four basic types of tea are distinguished by the process the leaf under goes. Leaves of Camellia sinensis soon begin to wilt and oxidize if not dried quickly after picking. The leaves turn progressively darker because chlorophyll breaks down and tannins are released. This process, enzymatic oxidation, is called fermentation although no true fermentation takes place. They want to stop the oxidation process at a predetermined stage by heating, which deactivates the enzymes responsible for bitter taste to produce different teas. In black tea this is done simultaneously with drying. The term "herbal tea" usually refers to infusions of fruit or of herbs (such as rosehip, chamomile or other fragrant leaves, petals or rind.)
White Tea
Young leaves (new growth buds) that have undergone no oxidation. The buds are shielded from sunlight to prevent formation of chlorophyll during growth. White tea is produced in lesser quantities than most other styles and can be more expensive than tea from the same plant processed by other methods. This is because extra time and attention goes into sheltering the leaf growth from the sun. It is less well known in countries outside of China, though this is changing with increased western interest in organic or premium teas.
Green Tea
The oxidation process is stopped after a minimal amount of oxidation by the application of heat, either with steam which is a traditional Japanese method, or by dry cooking in hot pans which is the Chinese traditional method. Tea leaves may be left to dry as separate leaves or they may be rolled into small pellets to make what is know as gun-powder tea. This process is time consuming and is typically done with pekoes of higher quality. The tea is processed within one to two days of harvesting.
Oolong Tea
Oxidation is stopped somewhere between the standards for green tea and black tea. The oxidation process takes two to three days. In China, semi-oxidized teas are collectively grouped as blue tea, literally: blue-green tea. The term "oolong" is used specifically as names for certain semi-oxidized teas and will have a slightly bitter taste compared to Green Tea.
Black Tea/Red Tea
These tea leaves are allowed to completely oxidize. Black tea is the most common form of tea in southern and in the last century many African countries including Kenya, Burundi, Rwanda, Malawi and Zimbabwe. In China it is called red tea because the actual tea liquid is red. Westerners call it black tea because the tea leaves used to brew it are usually black. However, red tea may also refer to rooibos. Rooibos is increasing in popularity in South African. The oxidation process takes between two weeks and one month. Black tea is further classified as either orthodox or as CTC (Crush, Tear, Curl), a production method developed about 1932).
Best methods for preparing each type of tea are:
Black tea
The water for black teas should be added at the boiling point (100 degrees C or 212 degrees F), except for more delicate teas, where lower temperatures are recommended. The most common fault when making black tea is to use water at too low a temperature. Since boiling point drops with increasing altitude, this makes it difficult to brew black tea properly in mountainous areas. It is also recommended that the teapot be warmed before preparing the tea. This is easily done by adding a small amount of boiling water to the pot, swirling briefly and discarding before adding the brewing tea. Black tea should not be allowed to steep for less than 30 seconds or more than about five minutes. After that, tannin is released, which counteracts the stimulating effect of the theophylline and caffeine which makes the tea bitter (at this point it is referred to as being stewed in the UK). Therefore, for a "wake-up" tea, one should not let the tea steep for more than 2-3 minutes. When the tea has brewed long enough to suit the tastes of the drinker, it should be strained while serving.
Green Tea
Water for green tea should be around 80 degrees C to 85 degrees C (176 degrees F to 185 degrees F). The higher the quality of the leaves, the lower the temperature of the water. Hotter water will burn green-tea leaves, producing a bitter taste. Preferably, the container in which the tea is steeped, the mug, or teapot should also be warmed beforehand so that the tea does not immediately cool down.
Oolong Tea
Oolong teas should be brewed around 90 degrees C to 100 degrees C (194 degrees F to 212 degrees F), and again the brewing vessel should be warmed before pouring in the water. For best results use spring or mineral water, as the minerals in spring water tend to bring out more flavor in the tea.
Premium or delicate tea
Some teas, especially green teas and delicate Oolong or Darjeeling teas, are steeped for shorter periods, sometimes less than 30 seconds.
VeggieSensations.com offers excellent electric and stove top Tea Pots and Kettles as well as Electric Hot Water Pots for heating the water for a perfect cup of tea. Larger teapots are a post-19th-century invention, as tea before this time was very rare and very expensive. Experienced tea-drinkers often insist that the tea should not be stirred around while it is steeping (sometimes called winding in the UK). This, they say, will do little to strengthen the tea, but is likely to bring the tannins out in the same way that brewing too long will do. For the same reason one should not squeeze the last drops out of a teabag; if stronger tea is desired, more tea leaves should be used.
Refrence: Wikipedia