Kefir is a fermented product that is drinkable due to its liquid nature, and may therefore be considered as a probiotic beverage. To create kefir, one uses starter cultures called kefir grains, which, despite the name, are not true grains - they are actually lumps of bacteria and yeast.
People commonly make kefir by fermenting dairy milk, which creates a slightly thick, sour product similar to yogurt or buttermilk. One may drink milk kefir as a beverage, consume it with cereals, or use it for cooking. It is also possible to make kefir by fermenting other liquids such as water, coconut water and non-dairy milk.