Both yogurt and sour cream are dairy products, and both are made from substances found in cow's milk. Both are tangy, and have a creamy white consistency. They can be used interchangeably in most recipes without significantly altering flavor or texture.
Sour cream is made by introducing bacteria into pasteurized light cream that has been separated from whole milk, states Ochef.com. Yogurt is made with fermented milk that has coagulated, which means that the solids have separated from the liquids. While sour cream is generally made with cow's milk, yogurt can be made from the milk of other animals, including goats and sheep. A cup of whole-milk plain yogurt contains 150 calories, while a cup of whole-milk sour cream contains nearly 500 calories, according to Calorielab.com.
The National Heart, Lung, and Blood Institute offers a standard Beef Stroganoff recipe that uses yogurt instead of sour cream. It can be found at this website:
The word yogurt comes from "yogurur," which is Turkish for "long life," according to strange-facts.info.