Hops:
This is another involved subject. There are many varieties of Hops, but they are divided into two main categories: Bittering and Aroma. Bittering Hops are high in Alpha Acids (the main bittering agent), typically around 10 percent. Aroma Hops are lower, around 5 percent. Several Hop varieties are in between and are used for both purposes. Bittering Hops are added at the start of the boil and usually boiled for an hour. Aroma Hops are added towards the end of the boil and are typically boiled for 15 minutes or less (Finishing). Hops can also be added to the fermenter, called Dry Hopping, but this is an advanced practice used during longer fermentations and will not be discussed here.
Published beer recipes often include a Hops schedule, with amounts and boil times specified. Other recipes specify the Hops in terms of AAUs and IBUs. AAUs are a convenient unit for specifying Hops when discussing Hop additions because it allows for variation in the Alpha Acid percentages between Hop varieties. For the purposes of this recipe, 7 AAUs are recommended for the Boil (60 minutes) and 4 AAUs for Finishing (15 minutes). This is assuming the use of Unhopped malt extract; if using Hopped, then only add the 4 AAUs for finishing. In this recipe, these amounts correspond to 22 IBUs for the boil, and 1.25 IBU for the finish. IBUs allow for variation in brewing practices between brewers, yet provide for nearly identical final Hop bitterness levels in the beers. This recipe is not very bitter.