The first of 4 major ingredients in your batch will be malt. Malt also contributes flavor and color to the finished beer. The second ingredient in your brew will be the hops. They are the female cone like flowers of the hop vine which impart bitterness, flavor, and aroma to beer.
Hops also are a natural preservative that inhibit some bacterial growth in a finished brew.
Packages should be marked with the Alpha Acid Rating. The AA rating multiplied by the ounces will give you the AAU or Homebrew units for the recipe. Yeast is the third ingredient in your beer. Yeast converts the fermentable sugars in your brew to alcohol and beer flavors. Different strains of yeast will produce the characteristics of an Ale or Lager.