Ad exchanges are platforms for buying and selling online inventory commonly known to many as ad impressions. Ad exchanges are extremely useful to buyers and sellers because it enables advertisers, agencies and publishers to buy and sell their ad impressions.
Ad Exchange connects not only to publishers but also to Ad Networks for online trading.
Ad Exchange that delivers multi-site by ad impressions.
Publisher supply their inventory to Ad Exchange when unsold the inventory; not guarantee how much your
inventory.
Basically, DSPs purchase instead of advertisers and agencies from Ad Exchange Inventory pool.