From Distillers Wiki
Low wines are a distilled product which is higher in proof than the original mash but quite lower in proof than the final spirit. Low wines can be thought of as an intermediate step in the manufacture of alcohol. Low wines are most commonly produced in low wine stills or stripping columns and are not potable due to the speed and inefficiency employed in their manufacture.
The most common use for low wines is in a traditional pot stills which do not have efficient columns and must use multiple distillations. Low wines are a concentrated mix which are used to produce the final high-proof spirit.