What is an algorithm, anyway?

Mashable's series Algorithms explores the mysterious lines of code that increasingly control our lives -- and our futures. An algorithm is a simple concept that, today, has many complex manifestations. Algorithms' central and opaque position at the heart of social networks like Facebook cause some to view algorithms in general with a sort of mystical reverence. Algorithms have become synonymous with something highly technical and difficult to understand, that is either an arbiter of objective truth, or, on the other end of the spectrum, something wholly untrustworthy. But when people refer to "the algorithm" -- whether Facebook's or another tech company's recommendation algorithm, or just "algorithms" in general -- do they really know what it means?