Herbal teas, technically known as herbal infusions, and less commonly called tisanes (UK and US /tɪˈzæn/, US also /tɪˈzɑːn/), are beverages made from the infusion or decoction of herbs, spices, or other plant material in hot water. Often herb tea, or the plain term tea, is used as a reference to all sorts of herbal teas. Many herbs used in teas/tisanes are also used in herbal medicine and in folk medicine.
These "teas" do not usually contain any true tea (Camellia sinensis), but some herbal blends do contain true tea (e.g., the Indian classic masala chai). The term "herbal" tea is often used to distinguish these beverages from "true" teas (e.g., black, green, white, yellow, oolong), which are prepared from the cured leaves of the tea plant, Camellia sinensis. Unlike true teas, most tisanes do not naturally contain caffeine (though tea can be decaffeinated, i.e., processed to remove caffeine).
A number of plants, however, do contain psychoactive compounds, such as caffeine or another stimulant, like theobromine, cocaine or ephedrine. Some have the opposite effect, acting as a sedative. Some common infusions have specific names such as mate (yerba mate) and rooibos (red bush). Hibiscus tea is one type of herbal infusion, but many described as some other plant have hibiscus as the main ingredient, or a major one. (Full article...)