All Teas Come from the Same Plant
All non-herbal teas actually come from the same plant, Camellia Sinensis, which originates and grows wild through all of south, southeast, and east Asia. White tea, yellow tea, green tea, dark tea, and black tea all come from this one type of tree. Herbal tea actually refers to any teas that are not made with C. Sinensis. (Pretty cool right? That’s a fun fact you can drop over a cafe meet-up with friends or over dessert at your next dinner party. You’re welcome.)
Similar to wine, awesome variety in humanity’s favorite drink comes from the specific terroir of where the trees are grown. Secondly, variety comes about in how it is processed, creating different levels of oxidation. Green tea was the first version: the green leaves were plucked, steamed, and dried. Later on, more steps like toasting, crushing, or panning the leaves allowed more oxygen and complex flavors before they were dried, darkening the colors over time. Black tea was the latest introduction to the scene- and the most oxidized.
Further variations, such as Darjeeling vs. Assam teas, actually refer to the regions they are grown in (in this case, both in India,) and you can get Darjeeling or Assam teas in green, white, yellow, oolong, and black varieties.
Other variations, like Earl Gray, get their unique flavor profile from the blend or post-production: Earl Gray mixes in bergamot oil from a citrus fruit in southern Europe. English Breakfast Tea is simply a black tea blend of Assam (in India,) Ceylon (in Sri Lanka,) and Kenyan teas. Sencha and Matcha teas are both Japanese green, Sencha is just brewed using the full tea leaves, whereas Matcha tea uses ground up tea leaves.