Beer was invented about 5000 years ago by a mistake. The mistake was that it was not invented earlier.
Beer is made of malt, water, hops and yeast, perhaps adjuncts, i.e., other starchy products which can develop alcohol by fermentation. Normally malt from barley is used. First it is boiled during which process the starch is converted into fermentable sugar types. After boiling it is strained in a lauter tun or a mash filter. The filtrate is boiled once again with addition of hops. After cooling down yeast is added and the beer is pumped to a fermenting vessel where the sugar is converted to alcohol. After fermentation the beer is filtrated and pumped to an intermediate tank, bright beer tank, from where it is filled into bottles, cans, kegs or tankers.

And then we drink it!