What is the difference between Ales and Lagers?

For those who care a little

Taste. Ales are more fruity and complex; lagers are generally crisper and cleaner in nature.

For those who care a lot, Ales (Sacchromyces Cerevisiae) ferment at a warmer (60-70 degrees F) temperature in a short amount of time (1-2 weeks). The warmer temperature produces esters which add to the complexity of the beer. Also, because the ale yeast are not very good at their jobs, they do not consume all of the sugars.

Lagers (Sacchromyces Carlsbergensis) on the other hand work at lower temperatures (45-55 degrees F). This slows down the metabolic rate of the yeast and therefore takes longer to consume the sugars (3-4 weeks). However, they are better workers and consume a higher percentage of the sugars. This makes the finished beer dryer, crisper and cleaner. Some lagers will have a small sulfur note.