Only Camellia sinensis is truly tea, though many other steeped beverages are commonly called teas.
A tisane is a steeped beverage made from a plant or plants other than the Camellia sinensis plant. These might include herbs, rooibos, flowers, dried fruits and spices. Some common tisanes include Camomile, peppermint and raspberry leaf "teas".
Tisanes are in no way inferior to tea, they are just different. In fact, tisanes can be a better choice of beverage in some situations. They generally contain little or no tannin (please note that tannic acid is one kind of tannin, but it is not the tannin found in tea), which means they don't become bitter when steeped for longer periods of time than tea leaves. Tisanes usually don't contain caffeine either, which can make them a better choice for evening enjoyment.
Don't make the mistake of assuming that all tisanes are safe for everyone. Natural does not automatically equal safe. Some are not considered safe for small children. Some can interact with medications, or may be harmful if you are pregnant, nursing or have certain medical conditions. In some cases, an herbal tisane might be safe in small quantities, but can become harmful if too much is consumed.
*Since I'm not a nutritionist or a doctor, I won't be making any sort of health claims about the teas and tisanes that I sell, nor can I recommend a tea or tisane to help you with a health problem that you may be experiencing. There is an ever-expanding array of herbal tisanes and blends being offered on the market, please be safe and research the safety of each ingredient before drinking.