<human>:  What is the difference between kefir and yogurt?
<bot>: The main difference between kefir and yogurt is in their preparation and fermentation. Kefir is a fermented milk product made with kefir grains, whereas yogurt is made by adding bacterial cultures to milk and allowing it to ferment. Kefir has a slightly sour, carbonated flavor and a thinner texture than yogurt. It also contains a higher concentration of probiotics than yogurt, and is thought to be more effective at promoting gut health.