Lager is a type of beer conditioned at low temperatures. Lagers can be pale, amber, or dark. Pale lager is the most widely consumed and commercially available style of beer. As well as maturation in cold storage, most lagers are also distinguished by the use of Saccharomyces pastorianus yeast, a “bottom-fermenting” yeast that also ferments at relatively cold temperatures. It is possible to use lager yeast in a warm fermentation process, such as with American steam beer; while German Altbier and Kölsch are brewed with Saccharomyces cerevisiae top-fermenting yeast at a warm temperature, but with a cold-storage finishing stage, and classified as obergäriges lagerbier (top-fermented lager beer).
Until the 19th century, the German word lagerbier referred to all types of bottom-fermented, cool-conditioned beer in normal strengths. In Germany today, it mainly refers to beers in southern Germany, “Helles” (pale) and “Dunkel” (dark). Pilsner, a more heavily hopped pale lager, is most often known as “Pilsner”, “Pilsener”, or “Pils”. Other lagers are Bock, Märzen, and Schwarzbier.
