The software that makes those decisions for each user, based on a secret ranking formula devised by Facebook that includes more than 10,000 factors, is commonly referred to as “the news feed algorithm,” or sometimes just “the algorithm.” On a social network with nearly 3 billion users, that algorithm arguably has more influence over what people read, watch and share online than any government or media mogul.

It’s the invisible hand that helps to make sure you see your close friend’s wedding photos at the top of your feed, rather than a forgotten high school classmate’s post about what they had for lunch today. But because Facebook’s primary goal is to grab and hold your attention, critics say, it’s also prone to feed you that high school classmate’s post of a meme that demonizes people you disagree with, rather than, say, a balanced news story — or an engrossing conspiracy theory rather than a dry, scientific debunking.