Let’s take an example for you to understand ‘fill rates’. If your website/app receives 100 visitors, the advertising program you are enrolled with will have to display 100 ads for these 100 visitors, correct? That act, the act of displaying 100 ads, is ‘fill rate’. Now, it may not be 100% because there aren’t many advertisers to display their ads on your website/app. Why this may be the case? Because your website/app may not have the theme they want to advertise in, or may not get an audience that could be interested in the advertisers’ products/services. So, in such instances, the advertising program you are enrolled with may not be able to display 100 ads, but may just be able to display 99 ads, or 98 ads, depending on the number of advertisers that want to display ads on your website/app. Good luck!
Feel free to follow me on Quora or my blogfor everything about marketing and advertising.