Kefirs are fermented milk drinks that have been around for centuries. They are made by adding a specific type of bacteria to milk, which causes the milk to ferment and produce a sour, tangy flavor. Kefirs are popular in many parts of the world, including Eastern Europe, Russia, and the Middle East. They are often enjoyed as a refreshing beverage or used as an ingredient in various dishes. Kefirs are also known for their health benefits, such as aiding digestion, boosting immunity, and providing probiotics.