Herbal teas, sometimes called tisanes, are blends of herbs, plants, or spices that are brewed like a tea. Occasionally, these mixtures also include a base tea, like a green tea, to balance their flavor and characteristics. Why don't we just call herbal teas 'teas', though? To understand that, we have to understand what a tea is!
Teas all come from one plant, Camellia Sinensis. As a result, if what is in your cup isn't from a Camellia Sinensis plant, it isn't a tea. The name Camellia comes from Georg Joseph Kamel, a Jesuit botanist who didn't discover tea, and Sinensis which means from China, which by many is regarded as the birthplace of tea. The leaves of this plant are withered, prepared, and then brewed to make a delicious cup of tea. Like all fine drinks, the terroir or environment in which a tea plant is grown gives it some flavor, as well as the preparation style.
So now that we know what a tea is, it's easy to understand what a tea isn't. It isn't any plant that isn't Camellia Sinensis. This is why popular herbs such as Hibiscus, Peppermint, Spearmint, Yerba Maté, and Rooibus are not considered pure teas, but instead herbal teas. They are grown from unique and different plants, and prepared in different ways. Sometimes, they aren't prepared at all, and are simply withered to help them last longer during transit and storage.
Herbal teas can be great to enjoy and brew the same way normal teas are. Typically, they should be brewed most similarly to a black tea. That is, at a temperature of 212 Fahrenheit or 100 Celcius for about 5 minutes. Typically they have strong flavors and are often blended together to make unique drinks. Keep your eyes peeling for herbal teas coming to Teavern soon!