Tea in this context refers to drinks made out of a specific plant: Camellia Sinensis. Interestingly both black and green teas are made out of that very same pla

Tea in this context refers to drinks made out of a specific plant: Camellia Sinensis. Interestingly both black and green teas are made out of that very same plant. It's mostly the post-processing that make them either green, black, oolong, pu-erh, etc. Just like there are different varieties of grapes more or less adequate to produce some kind of wines, there are different varieties of Camellia Sinensis. All varieties of Camellia Sinensis were thought to contain caffeine, until this specific variety was (re-)discovered. Herbal teas are basically infusions of any plant that's not Camellia Sinensis.