All beers are made as ales or lagers; ale and lager are the two main branches (classifications) of the beer family tree and are closely related branches at that. Ales are the older, distinguished, traditional brews of the world, predating lagers by thousands of years, whereas lagers are a relatively modern creation, less than 200 years old.
Yeast makes the beer
The branch of the beer family tree — ale or lager — corresponds to the type of yeast used to ferment the beer. You have ale yeast and lager yeast, and these types of yeast, in turn, typically dictate the temperature at which the beer is fermented. Ales are traditionally fermented at warmer temperatures (55 to 70 degrees Fahrenheit, 12 to 21 degrees Celsius), while lagers are typically fermented at cooler temperatures (38 to 50 degrees Fahrenheit, 3 to 10 degrees Celsius).
The cooler fermentation and aging temperatures used with lager yeast slow down the yeast activity and require a longer maturation time. The cold environment inhibits the production of fruity aromas (called esters) and other fermentation byproducts common in ales. This process creates the lager’s cleaner taste. Long aging (or lagering) also acts to mellow the beer.
You can taste the difference, sometimes
Every beer beginner wants to know how ales taste different from lagers. If only it were that easy! This question is sort of like asking how red wines taste different from white wines.
Ironically, you can find beer styles called red beer and white beer, but that’s another story altogether, and you can be sure that it doesn’t involve grape skins.
Ales share many common characteristics, and so do lagers, but the two groups overlap so much that any absolutes about either class are usually wrong. This overlap creates some confusion and the need for experts to explain the different characteristics, but it also creates the need for beer exploration.
You can say that ales generally
Include more robust-tasting beers
Tend to be fruity and aromatic
Include more bitter beers
Have a pronounced, complex taste and aroma
Are enjoyed warmer (45 to 55 degrees Fahrenheit, 7 to 12 degrees Celsius)
And you can say that lagers generally
Include lighter-tasting beers
Tend to be highly carbonated or crisp
Tend to be smooth and mellow
Have a subtle, clean, balanced taste and aroma
Are served fairly cool (38 to 45 degrees Fahrenheit, 3 to 7 degrees Celsius)
If someone says, “I don’t like ales,” or “lagers give me headaches,” respond by saying that simply too much variety exists for that kind of distinction to hold water (or beer, for that matter). Beer exploration is called for!