Yoghurt (or yogurt) is the result of milk, usually cow's milk, that has fermented and coagulated after friendly bacteria have been added in a controlled environment. The end result is a creamy-textured yoghurt with an astringent, slightly tart taste. In commercial yoghurt Lactobacillus bulgaricus or Streptococcus thermophilus is the most widely used bacteria.
Plain yoghurt is made from whole milk, low-fat or non-fat milk without additional flavoring ingredients. Flavored yoghurt has sugar, chunks of fruit, fruit juices and/or artificial flavorings added. The fruit can either be on the bottom or be already stirred in (Swiss-style yoghurt). Some flavored yoghurts contain gelatin or stabilizers for a thicker texture.
Yoghurt is a good source of B vitamins, protein and calcium and is much more digestible than fresh milk. It's also said to keep the intestinal system populated with good bacteria and therefore in healthy condition.
Frozen yoghurt resembles soft-serve ice cream in texture and is usually flavored with fruit or artificial flavorings.