I collect ginger beers, they are more common up here in canada, the drink was a mildly alcoholic sort of gingerale popular in England. Soldiers got to like it during WWI and it gained some popularity here too.
Xaquin,
My understanding is that it was a 'small' beer. In other words, the contents were fermented (that is, the product contains alcohol) but to a lesser extent than regular beers. It contained maybe 2-3 % booze - half of what other beers might. For certain, this affected the flavor but other than that, it probably was similar to ginger ale.