Malted barley is seeped with hot water to create a 'mash'
This produces a sugar solution known as 'wort'.
The wort is boiled vigorously to reduce the size of the sugar molecules and make them easier to digest for yeast. At the end of the boil, and sometimes also at the beginning, hops are added to the wort which imparts unique flavours into the liquid, depending on the variety of hop, length of time in the solution and the temperature of the solution.
The wort is cooled and sealed into a fermenting vessel, after the addition of live yeast. The yeast digests the sugar in the wort (in a temperature controlled environment) releasing carbon dioxide and alcohol as a by-product.
The majority of the yeast floats and can be skimmed off the top of the beer when the desired alcohol percentage is reached. The remaining yeast will sink to the bottom and can be left behind when the final product (beer) is drawn from the vessel.