Ad inventory
Ad inventory is the total amount of advertising space a publisher puts up for sale. The term originally came from print media, but now it primarily refers to internet ad space. Ad publishers can sell inventory to marketers in multiple formats, including desktop websites, mobile websites, mobile apps, and video ads.
Increasingly, app marketers buy ad inventory through advertising exchanges and intermediary markets. This ties in with programmatic advertising, which is when marketers use software to buy ads. Traditionally, you bought ads by manually contacting representatives at a publisher, but now you can buy ads with algorithmic software. As a result, marketers can purchase ad inventory much more quickly as it becomes available.