An online service that allows advertisers to advertise their services for sale on multiple platforms. This area represents different items across many websites. Ad inventory is generally more valuable at certain times. This can depend on the day of the week, the time of day, or even what channel you're advertising on. The funding model of your ad network is determined by how many times the ad gets shown and how much you get paid. Some examples are CPM (cost per thousand impressions), CPC (cost per click) and CPA (cost per acquisition).