As an Englishman, tea is part of my life.
Tea is an infusion of the leaves of the tea plant. I'm thoroughly ignorant as to the difference between "green" and "black" teas, although I'd have thought it was a question of immature and mature leaves.
Green tea is very popular in Japan and China, to mention just a couple of countries, whilst the "black" tea is brewed in India and drunk, frequently, with milk and/or spices, where it is known as "chai".
"Tea" made with chamomile, lemongrass, cinnamon, St John's Wort, ginger, dandelion, mint leaves or grass from the back lawn is not,strictly, "tea"; it's an infusion.
Green tea has been credited with many healthy attributes. All I can add is that tea,according to the English, resolves all worldly problems.
" WHAT? Your business went bankrupt??? Never mind, dear, have a cup of tea."
" You mean, she just walked out on you? Well, well - have a cup of tea, luv, and you'll feel better".
The very best tea to purchase is leaf tea - NEVER buy tea bags unless you are desperate. You might find tea from India ( Assam is very good); Ceylon (Sri Lanka) - a little milder; Kenya; China, Japan...
My preference is for Assam and for a curious smoked tea from China called Lapsang Souchong.