Dry hopping is the process of adding hops late in the process, usually in the primary fermenter after fermentation has completed or into a secondary fermenter. It is meant to add extra hop aroma without imparting too much bitterness to the final beer.
Kraeusen is the name for the darker, spotted, almost rocky head of foam that forms on the surface of the wort during the fermentation period. It often forms a ring on the fermentation vessel even after the beer has completed fermentation.
The term alcohol when applied to beer is really just a synonym for either ethyl alcohol or ethanol. Most craft beer styles range between 3.2% to 10% alcohol by volume (ABV), although some are even lower or higher than that.
Bottle conditioning is the process through which beer is naturally carbonated in the bottle as a result of fermentation. Usually this is accomplished by adding a priming sugar during the bottling process.
A naturally occurring soft resins in hops. Alpha Acids are converted during wort boiling to iso-alpha acids, which adds bitterness to beer. Over time alpha acids will age out (through oxidation) and bitterness will lessen.