If you look on the containers of buttermilk, the lowfat has fewer calories and fat grams. Most of the buttermilk found in supermarkets is cultured buttermilk, made by adding a bacterial culture to low-fat or nonfat milk. Churn buttermilk is the liquid that remains after milk is churned into butter.
The three kinds of buttermilk that I typically see in our stores is Cultured Buttermilk, Low-Fat Cultured Buttermilk, and Country Style Cultured Buttermilk that has butter flakes added. Cultured may or may not be on the front label, but "cultures" is included on the ingredient panel.
KY Kate