From the Wikipedia page 
A tea ceremony is a ritualised form of making tea. The term generally refers to either chayi or chadao Chinese tea ceremony, chado or sado Japanese tea ceremony, tarye Korean tea ceremony. The Japanese tea ceremony is more well known, and was influenced by the Chinese tea ceremony during ancient and medieval times. One can also refer to the whole set of rituals, tools, gestures, etc. used in such ceremonies as tea culture. All of these tea ceremonies and rituals contain "artificiality, abstractness, symbolism and formalism" to one degree or another.
These rituals can be found worldwide, although are centred on Asia and Europe, including the Victorian-era 'high tea' or afternoon tea ritual, where the ritual of being seen to have the right equipment, manners, and social circle, was just as important as the drink itself.
At a very basic level, tea ceremonies are a formalized way of making a hot drink, in a process which has been refined to yield the best taste. The Royal Society of Chemistry's Dr. Andrew Stapley has written about the chemistry behind brewing tea, and some traditional ceremonies using leaf tea appear to closely mimic his suggested method, including the idea of synchronizing ones' actions with the temperature of the water.