Originally, buttermilk was the liquid left behind after churning butter out of cream. This type of buttermilk is known as traditional buttermilk.
The term buttermilk also refers to a range of fermented milk drinks, common in warm climates (e.g., the Middle East, Turkey, Afghanistan, Pakistan, India, Sri Lanka and the Southern United States) where unrefrigerated fresh milk sours quickly, as well as in colder climates, such as Scandinavia, Finland, Netherlands, Germany, Poland, Slovakia and Czech Republic. This fermented dairy product known as cultured buttermilk is produced from cow’s milk and has a characteristically sour taste caused by lactic acid bacteria.