Lagers are on one branch of the beer family tree, with ales on the other. Lager beers are made with a particular kind of yeast that ferments at cooler temperatures than ale yeast. This yeast also ferments much at a much slower pace, so the beer is stored (or "lagered") for much longer than ales before being ready to drink.
The long fermentation time leads to cleaner, smoother flavors in the finished beer. Malt and hops flavors tend to predominate with extremely little or no fruitiness from the yeast.
• Pilsners - Typically gold in color, with sweet caramel malts and herby or spicy hops. Pilsners should finish very clean and crisp, and the beer should feel refreshing on the palate. Try Pilsner Urquell, Lagunitas Pils, and Harpoon Pilsner.
• Helles - A bit more malty than pilsners, but with a similar clean and refreshing flavor. They are also pale gold with a crisp finish. Try Victory Lager and Paulaner Original Müncher.
• Oktoberfest - Also called märzen beers, this style is normally heavy on the caramel malts with little or no hops presence. They're deep amber in color and medium bodied. Try Sam Adams Octoberfest, Paulaner Oktoberfest Märzen, and Widmer Oktoberfest (generally only available in the fall).
• Dunkels - Rich and hearty, this beer is also very heavy on the malts, but has more roasted flavors than the Oktoberfest. It's typically dark brown or ruby in color with medium body. Try Ayinger Altbairisch Dunkel and Harpoon Munich Type Dark Beer.
• Maibocks - Also called heller bocks and golden bocks, these amber-gold beers have a good amount of hops to balance their creamy maltiness. They finish a bit bitter and have a full-bodied feeling to them. Try Smuttynose Maibock and Sierra Nevada Glissade.
• Bocks - These beers have a lot of roasted malt character to them with just a bit of hops for balance. They're dark brown and generally very full-bodied. Try Anchor Bock and Leinenkugel 1888 Bock.
• Doppelbocks - Also called double bocks, these are an amped up version of bock beers. The malts are generally more complex and heavy with very little hops presence. Try Tommyknocker Butthead Doppelbock and Ayinger Celebrator.
Which lager styles do you love? Any particular beers to recommend?
Related: How Cold Should Beer Be Served?