Kefir is a fermented dairy product that has been enjoyed for centuries. It is traditionally made by fermenting cow's milk or goat's milk with kefir grains, which are small clusters of bacteria and yeast. Kefir is known for its tangy flavor and creamy texture, and it is also packed with probiotics, which are beneficial bacteria that promote digestive health. While kefir is the most common term for this beverage, there are some synonyms you may come across, such as yogurt drink, cultured milk, and fermented milk. These terms all refer to a similar product, but they may have slight differences in preparation or composition, depending on the region or culture in which they are produced.