Lager is a type of beer conditioned at low temperatures. The term may also be used as a verb to describe the cold-conditioning process.
Lagers can be pale, amber, or dark. Pale lager is the most widely consumed and commercially available style of beer. Well-known brands include Pilsner Urquell, Miller, Stella Artois, Beck's, Brahma, Budweiser Budvar, Corona, Snow, Tsingtao, Singha, Kirin, Heineken, Carling, Foster's, Carlsberg, Birra Moretti and Tennents.
As well as maturation in cold storage, most lagers are also distinguished by the use of the 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 a 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 (de) referred to all types of bottom-fermented, cool-conditioned beer, in normal strengths. In Germany today, however, the term is mainly reserved for the prevalent lager beer styles of 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. In the United Kingdom, the term "lager" commonly refers to pale lagers derived from the Pilsner style.