Tea Basics

So as I talk to more and more customers I realize they need some basic information about tea.  I have been studying tea for a quite a few years and consider myself a novice.  Yet I am still miles ahead of the average tea drinker.
All tea, true teas, are made from the same plant, Camellia sinensis.  It is a relative of the flowering Camellia japonica found in many yards.  There are two main varietals, Camellia sinensis sinensis and Camellia sinensis assamica.  The Camellia sinensis sinensis is largely considered the Chinese varietal, and the assamica is the Indian varietal.  Then like most plants there are further varietals that are better adapted to altitude, rocky soil, more moisture, less moisture, etc.  There are tea plantations in Hawaii and in South Carolina.  The plants can grow here, but it is labor intensive, so it hasn't taken off as a cash crop.  Although there are increasing numbers of tea gardens in Hawaii.

There are five major tea groups, I know that I will probably get some arguments on this one, but I am going to include the following as my 5 main groups.
White
Green
Oolong
Black
Pu'erh
White teas originated in China, some say they still have to come from China to be white tea.  White tea is air dried.  Some consider it to be semi-oxidized because some bruising does happen to the leaf during the drying.
Green teas are pan fired (Chinese style) or steamed (Japanese style) to stop the oxidation & keep the green in the leaf.
Oolong teas are from 5 to 95% oxidized teas.  Mainly found in China & Taiwan.  There are two main leaf styles, long twisted leaves or balled.
Black teas are considered 100% oxidized.  They are produced in India, Sri Lanka, China, Japan, Kenya.
Pu'erh teas (pronounced like pour, some say poo-air) are fermented teas.  Either artificially, shou (pronounced show), or over time, sheng style.  These teas continue to change flavor and are considered enigmatically alive.  These teas come from Yunnan, China.
There are health benefits to all teas, but I hesitate to get too involved in listing the benefits, because some of them are not recognized in the US.  The benefits I will list are that teas contain anti-oxidants and caffeine.  Caffeine can help in weight loss and anti-oxidants are immune boosters.
There are other classes of tea, like yellow, dark and semi-oxidized that don't fall into the oolong group due to differences in production.
Now that you are completely confused.  I'll try to explain a few things.
All of the 5 groups of teas have many variations in them, like wine makers with wine.  They start out with a merlot grape, but two different winemakers will make completely different tasting wine with them.  The same could be said of tea.  Each tea master has his own way of doing things, and they will change slightly with each harvest to get the final taste profile that they are trying to achieve.  So a white tea from one garden will taste different from another gardens white tea. 
Oxidation is what happens when you break the cell wall of the leaf and expose the leaf to air.  Like a bite out of an apple makes the inside turn brown.
Fermentation is the process that moisture and heat cause the leaf to break down.  The Shou Pu'erhs are put into a pile and like compost they heat up and start breaking down through enzyme activity.  Sheng Pu'erhs take years to age and taste like the cooked pu'erhs do after a few months. 
Tea bags usually have smaller pieces of tea, so they can open up faster in the water and make a strong cup of tea.  They don't have the flavor nuances of specialty loose leaf tea.  They also don't re-steep very well.
The more you start to learn about tea, the more you learn that it is just the first step on a delicious and varied journey.  Start exploring!