For purposes of distillation, beer is another name for wort. Beer made for the purpose of distillation is in general not boiled and does not contain hops. It would be considered unpalatable by any drinker of commercial beer.
Mashing wort for the purpose of distillation is different than for beer to be drunk. Distillers aim to maximize the fermentable sugars from the source materials. Unfermentable sugars left in a wort will not carry over or flavor the distillate. It is considered to be a waste. The mashing process for distillers will normally be a single step with a saccharification rest at a low temp (140-145f) to maximize fermentable sugars.
Distillers tend to distill their beer quickly after fermentation has stopped. As there is less need to worry about infections, distiller's beer does not require Pasteurization by boiling. For some styles, bacterial infection is even encouraged, such as Lactobacillus and Acetobacter infection.