@Beregorn
Beer is made from a starch source and yeast. The starch source (wheat, corn, or even rice) is boiled in water which breaks down the starches into smaller sugars (Starch is just a long chain of sugars). Yeast is then added to convert those sugars into alcohol.
Prior to 1960, beer had to be pasteurized (heated until all microbes were killed) if it was to be canned or bottled. This was done in order to kill off the yeast present inside the beer which would continue fermenting the beer once inside the container. Over-fermenting beer gives it off flavors and changes the ABV, meaning that products wouldn't be consistent between batches if unpasteurized.
Once the Space Race happened in the 1960's, technologies created through NASA began to filter out into the commercial world. One of these technologies was "Micro-Filtering", the ability to filter very specific things from their source liquids. NASA had been using micro-filtration to filter water out of astronaut's urine and sweat in order to recapture it as drinking water in space. Micro-filtration hit the brewing world like a bomb and was quickly adopted in order to filter yeasts out of their finished beers.
Beers became incredibly consistent and shelf life improved drastically because of micro-filtration. Because the beers were no longer being heated once finished they were called 生ビール "Nama Beer" or "Raw Beer". Virtually every beer you drink nowadays is a "Raw" Beer, the technology has become that widely accepted.
https://japandaily.jp/whats-so-nama-about-nama-beer-691/