What Is The Difference Between A Lager And An Ale?

For the average beer drinker, the difference between an ale and a lager comes down to how the beer looks, smells, and tastes. Ales tend to be fruity-estery, while lagers are clean-tasting and frequently described as 'crisp.'

But to a brewer, the difference is more fundamental than that. It's not color, or flavor, or aroma, or hop/grain/malt varietals or even water hardness that separates a lager from an ale.