For the most part, the answers are straightforward. "Advertisers pay to have their ads shown in front of YouTube videos," says Markiplier, who currently has 21 million subscribers for his gaming videos. "You get a share of that." Determining that share, however, is a little more complex. "It's like this: You have a fraction of an amount. There's a bunch of factors outside of that, that have nothing to do with you, that affect whether that fraction is bigger or smaller," adds Hannah Hart, whose longstanding channel has some 2.5 million subs. Beyond that there are merch deals, collaborations with brands, and other promotions YouTubers can use to bring in cash from their channels.