What is two-stage fermentation and what are its advantages?

Two-stage fermentation, is fermenting by using two fermenters, instead of one, to make your beer. Most brewers will start in a plastic bucket, also called a primary (fermenter). Then, they will transfer the beer into a glass carboy, or secondary. So, why would you want to take this extra step? The main reason is for clarity. The main purpose of the secondary vessel is to facilitate the settling of the yeast and to allow the beer to age.

This extra step will go a long way in helping with the clarity of your beer, and the flavor will improve as well. The flavor improves because a lot of that sediment can be bits of grain or hops, which can leave an off flavor in your beer. So, if you are looking to make the best beer possible, you have to transfer the beer at least once.