The bitterness derives from an acid, alpha acid, in a resin called lupulin. Hops can be purchased whole, in pellets or as an oil. Everyone has their own preference. They can also easily be grown in your own yard . You just need a trellis or several poles, and a love for the pungent odor.
Yeasts are responsible for turning the wort into beer through a process of fermentation.
Basically there are two types of beer yeast- lager and ale. Ale yeast tends to ferment at higher temperatures and to flocculate at the top of the beer. Lager yeast performs well at lower temperatures and sinks to the bottom once fermentation has started. Some would prefer finding a nice microbrewery or brewpub , while others like to explore the history of beer in Europe .