Caffeine is a stimulant found in many beverages, and the term 'caffeine source' refers to the drinks that contain it. TEA, cola, and kola are all sources of caffeine, with TEA being the most common. TEA is a beverage made from the leaves of the Camellia sinensis plant, and is usually served hot or iced. Cola is a carbonated soft drink that is flavored with extracts from the kola nut, and is one of the most popular drinks in the world. Kola is a type of nut native to tropical Africa, and its extract is used to flavor many different types of beverages. All three of these drinks are sources of caffeine, and can provide a boost of energy for those who consume them.