Beer styles are divided into the two main groups of Ales and Lagers. While there are many differences between the two, the most important distinction is the flavor. Generally ales have more fruity, robust flavors than lagers while lagers can be more crisp and subtle. Ales are often referred to as being "top fermented" by the way they stay on top of the beer during primary fermentation and Lagers are referred to as "bottom fermented" because lager yeast tends to settle to the bottom and ferment.
The Lager style of brewing developed in the cold mountainous regions of central Europe. This style accounts for over 90% of the beer brewed in the world. Largely it is a clear, pale beer fermented with bottom-fermenting yeast at cooler temperatures. Lager yeast will ferment at cooler temperatures than ale yeast, in the 40 to 50 degree range, and can remain active to near freezing. They usually are then aged at cold temperatures. The fermentation period is longer than it is for ales, hence the name, which in German means 'to store'. The resulting beers display malt and hop flavors that are free from the fruity and estery traits often found in ales. However, fermenting with lager yeasts at warmer temperatures can result in ale-like qualities. Also, when not properly aged they can exhibit definite sulfur notes.
The following, from light to dark, are the major families of lagers:
American pale lagers are normally not 'all malt' beers and the malted barley is supplemented with adjuncts or cereal grains such as corn or rice. They range from the low calorie light beers and American premium beers to the higher alcohol ice beers and malt liquors. In most cases the hop character is subdued.
European pale lagers are usually brewed with less, if any, adjuncts than the mass produced American light lagers and can range from the hoppier pilsner style to the helles (light or pale in German ) style, to export styles.Pilsner has a broad and loose interpretation. Classically, it has a dry malt character followed by a flowery hop bouquet, is straw to gold in color and has an alcohol content of 5% abv. Too many brewers take it lightly, in more senses than one. In their all-around interpretation, it is the German brewers who take the style most seriously, inspired by the original pilsners of the Czech Republic. Some large-scale American brewers who call their beer(s) a "fine pilsner" are missing the mark.
American amber and red lagers are amber to light reddish in color and can exhibit a caramel flavor with little hop character. Some craft brewers do make a hoppier version of this style.
California common or steam beer is amber to copper in color and is fermented as a lager at ale temperatures. This style developed during the California gold rush and was resurrected by the Anchor Brewing Co. of San Francisco.
German Marzen (March in German), Oktoberfest, and Vienna lagers are characterized by toasty malt flavors, medium body and low to medium hop character. They are amber to reddish in color and around 5 to 5.5% abv.
Dark lagers can be dark amber to brown in color and are sometimes called "dunkel' after the German word for dark. They can be characterized by caramel to chocolate flavor and are low to medium in hop character.
Bock is the German term for strong beer and is sometimes symbolized by a goat on the label. In Germany, a bock beer has more than 6.25% abv and can be deep gold to tawny brown in color.
Maibock (May in German) is a beer of super-premium quality that is released in early May to celebrate spring. They are usually deep gold in color with a solid malt flavor and medium hop finish and come in around 6.5% abv.
Doppelbock means double in Germany or extra strong and are tawny or dark brown in color. They are usually released in March or April and come in around 7.5% abv. They usually are characterized by a very full, rich malt flavor with a somewhat sweet finish and low hoppyness. Their names usually end in "ator"
Eisbocks are dopplebocks in which potency is heightened by a process of freezing. Because water freezes before alcohol, the removal of ice (eis) concentrates the beer.