Inventory is the supply side of advertising
In an advertising marketplace, inventory represents the available opportunities that advertisers can purchase.
Publishers create this supply through their websites, pages and advertising placements.
Not all inventory is equal
Two websites can generate the same number of impressions while producing very different commercial value. Audience relevance, placement quality, traffic legitimacy and advertiser demand all matter.
Inventory and demand
Inventory only becomes monetizable when there is demand for it. This is why marketplace participation can be important: publishers gain access to advertisers that may value their particular inventory.