The word yogurt comes from a Turkish word meaning to curdle or to thicken. It can be spelled yogurt, yoghurt, or yogourt, with yoghurt being more commonly used in Australia.
Originally a simple fermented dairy product, yoghurt now has many variations and characteristics. It can be thin and runny, or thick and firm. It can be made from cow milk, goat milk, sheep milk, nut milk, soy milk, rice milk, and from many other creamy, protein-rich substances.
Yoghurt is the product of beneficial bacteria fermenting milk and turning it into a thickened, acidic food that will stay fresh longer than milk itself. It also contains millions of bacteria that are "friendly" to the human gut.
Like yoghurt, kefir is a thickened and fermented milk product. The difference bewteen yoghurt and kefir is that various strains of yeast also take part in the fermentation process. It has a slightly sour flavor and sometimes a faint effervescence.
Not only do yoghurt and kefir contain the same amount of protein and fat as the milk from which they are made, they also contain calcium, riboflavin, vitamin B6, and vitamin B12.