So to state the obvious: lager and ale are both types of beers, that is they are fermented from grain. But the real question is, what’s the difference between the two? The major difference between the two is the yeast that the beer is brewed with.
S. cerevisiae is the most common yeast found, in which it is used in things such as breadmaking and winemaking. It is the original or natural beer yeast used in ale beer production, known as the “top-fermenting” or “ale” yeast.
This yeast ferments throughout the body of the beer wort and rises to the surface, where it can be harvested. After a while, it will sink to the bottom of the vessel, remaining after the finished beer is removed. This yeast has a greater tolerance to alcohol than others yeasts, therefore creating higher alcohol content beers.
Saccharomyces uvarum is known as the “lager” or “bottom fermenting” yeast. It also ferments through the body of the beer wort, but instead of rising to the surface like the “ale” yeast, it settles to the bottom of the vessel, making it very fragile because it converts the sugar to alcohol slower and at a lesser extent.
This type of yeast has a much lower alcohol content and works better at cooler temperatures compared to the more popular choice.