different beers can have different natures, depending on the ingredients used; for example, an ale uses top fermenting yeast. top fermenting yeasts eat more sugar and produce more alcohol. a lager uses bottom fermenting yeast. bottom fermenting yeasts eat less sugar and produce a crisper, cleaner taste. adding hops makes the beer more bitter and aromatic. specialty malts (different types of cooked barley) produce different flavours and colours. these flavours and colours are most notable in dark beers like porter and stout.