Strained yogurt,
Greek Yogurt,
yogurt cheese, sack yogurt or kerned yogurt is yogurt that has been
strained to remove most of its whey, resulting in a thicker
consistency than normal unstrained yogurt, while still preserving the
distinctive sour taste of yogurt.
Like many types, strained yogurt is often made from milk enriched by
boiling off some water content, or by adding extra butterfat and
powdered milk. In Europe and North America, it is often made from
low-fat or fat-free cow's milk. In Iceland, a similar product named
skyr is made.
Read more on Wikipedia