What is "cultured" buttermilk?

[Pinky Tuscadero]

How is it different from the liquid that is left when you make butter?

[snugglebug14]

The liquid left from making butter is old fashioned buttermilk. Nowadays, cultured buttermilk is milk that has had a live culture added to it. If you're making it at home you then let it sit out so that the bacteria culture can go to work. In the end you have a much thicker form of milk. For many people it is far easier to digest.

something i've ben wondering is if you are making cultured butter could you take the liquid left at the end and somehow make that into "cultured buttermilk"? if not what uses are there for that liquid leftover at the end?