A finite, exact procedure — a recipe of steps that, followed mechanically, produces a result. Algorithms predate computers by more than a millennium, but the word acquired a second life as the name for the opaque ranking, recommendation, and decision systems that now sort social feeds, set prices, screen job applicants, and allocate risk across modern life.
There is a word you probably used today without thinking about it. You said the algorithm did this, or the algorithm showed you that. But the word is doing two very different jobs at once. In mathematics it means something humble: a precise list of steps that anyone or any machine can follow to get a result. In ordinary life it has come to mean something far more powerful — the unseen system that decides what you see, what you pay, whether you get the job. The same word covers a long-division procedure and a system that shapes billions of decisions a day. That distance is the story of what happened when humanity took its most disciplined tool and handed it enormous power.