What is Kefir?

I quote here from The Spruce Eats, a great source of food history and lore: Kefir is a fermented milk product similar to yogurt. It has its origins in the Caucasus Mountains of Russia. This tangy, creamy milk product is sometimes referred to as the “champagne of milk” because of its fizzy effervescence. The natural carbonation gives kefir a light, foamy, creamy texture, even when made with low-fat milk. Yogurt vs. KefirYogurt and kefir differ based on the type of cultures used to ferment the milk. Yogurt uses only bacteria, primarily Lactobacillus species, while kefir uses both bacteria and yeast. While yogurt can range in texture from a thick liquid to a semi-solid, gel-like consistency, kefir is primarily liquid. Kefir is traditionally fermented at room temperature, and a family would let the milk ferment overnight. Yogurt is often fermented in a warmer environment.