At AdThrive, we have the most sensitive ad categories blocked automatically, because we like to make the internet a little bit safer for families.
Beyond that, every time a reader goes to your website, a giant pool of advertisers has an opportunity to bid for the right to serve their ads on your site. Whoever bids the most money wins, and gets to advertise in that ad space for that pageview. It's all decided by technology in the blink of an eye, so AdThrive doesn't choose your advertisers for you, and we don't even know who will win each competition and serve on your site before it happens.
The advertisers are bidding based on two major factors:
1. The content on your site. If you have a food blog, you're more likely to get food-related advertisers bidding for your ad impressions.
2. The browsing history of your readers. If your readers have been searching online for a car, for example, they might see car-related ads on your site, even if your blog is completely unrelated to car-buying. This means that the ads YOU see will typically be very different than the ads your readers see. (You'll see ads based on your own browsing history; your readers will see ads based on their personal browsing history.)