Not really clickbait. Well kind of, but the article is fairly thorough at a high level. "Pure energy" in this case is the bacteria are able to obtain electrons

Not really clickbait. Well kind of, but the article is fairly thorough at a high level. "Pure energy" in this case is the bacteria are able to obtain electrons directly from their environment in order to power their internal chemistries that are needed for all cells to continue functioning. Those chemistries involve repair and reproduction mainly. The key difference to all other known biology is that while all cells (singular or part of animals) use electrons for repair and reproduction they get from ATP.