When people pay attention, not only are they engaged, which is great for Google, but they’re also likely to share and comment on your work. These are all indications of engagement. And those share links help you considerably as long as they’re real and they’re organic. You can’t just go out and buy shares or engagement. You won’t make any traction like that.
Perhaps the most popular network for placing these types of ads is Google AdSense. With this program, you do not need to be in direct contact with advertisers; you simply place the banner on your site, Google chooses ads relevant to your content, and your viewers click on the ads. There are countless similar programs available if you find that AdSense doesn’t work for you, such as Chitika, Infolinks, and Media.net.