Beer styles all fall into two broad types, determined by the time and temperature of the primary fermentation as well as where the yeast sits during fermentation. These are ales and lagers.

Ale

Ale is beer that is brewed using only top-fermenting yeasts, and is typically fermented at higher temperatures than lager beer (15–23°C). Ale yeasts at these temperatures produce significant amounts of esters and other secondary flavour and aroma products, and the result is a flavourful beer with a slightly "flowery" or "fruity" aroma.

Styles of ale include Barley Wine, Belgian Trippel, Belgian Dubbel, Altbier, Bitter, Amber Ale, Brown Ale, Pale Ale, Kölsch, Porter, Stout, and Wheat beer.

Lager

Lagers are the most commonly consumed type of beer in the world. Lagers are of Central European origin, taking their name from the German word ‘lagern’ ("to store"). Lager yeast is a bottom-fermenting yeast, and typically begins fermentation at 7-12°C (the "fermentation phase"), and then stored at 0-4°C (the "lagering phase"). During the secondary stage, the lager clears and mellows. The cooler conditions also inhibit the natural production of esters and other byproducts, resulting in a "crisper" tasting beer.

Most of today's lager is based on the Pilsner style, pioneered in 1842 in the town of Pilsen (Plze?), in an area of the Austrian monarchy now located in the Czech Republic. The modern Pilsner lager is light in colour and high in carbonation, with a strong hop flavour and an alcohol content of 3–6% by volume. The Pilsner Urquell or Heineken brands of beer are typical examples of pilsner beer.

Styles of lager include American-style lager, Bock, Dunkel, Helles, Märzen, Oktoberfest, Pilsner, Schwarzbier and Vienna lager.

Hybrid beers

Hybrid or mixed style beers use modern techniques and materials instead of, or in addition to, traditional aspects of brewing. Although there is some variation among sources, mixed beers generally fall into the following categories:

• Steam beers were invented by German immigrants living in California and are made with bottom-fermenting (lager) yeasts, but fermented at warmer (ale) temperatures. The name "steam beer" is a trademark of the Anchor Brewing Company, though other brewers brew this beer under the designation "California common".
• Fruit and vegetable beers are mixed with some kind of fermentable fruit or vegetable adjunct during the fermentation process, providing obvious yet harmonious qualities.
• Herb and spiced beers add herbs or spices derived from roots, seeds, fruits, vegetables or flowers instead of, or in addition to hops.
• Wood-aged beers are any traditional or experimental beer that has been aged in a wooden barrel or have been in contact with wood (in the form of chips, cubes or "beans") for a period of time (Oak is the most common). Often, the barrel or wood will be treated first with some variety of spirit or other alcoholic beverage--bourbon, scotch and sherry are common.
• Smoked beers are any beer whose malt has been smoked. A smoky aroma and flavour is usually present. The most traditional examples of this style are the Rauchbiers of Bamberg, Germany. However, many brewers outside of Germany--most notably American craft brewers--have been adding smoked malt to porter beers, Scotch ale and a variety of other styles.