A daisy chain is a chaining of ad-networks used to optimize ad revenues.
In daisy chaining, a floor CPM or flat fixed CPM is assigned for each ad network. The ad network with the higher agreed CPM is number one in the daisy chain flow. If the number one ad network can’t deliver an ad creative above or equal to the floor price, it operates a passback and the ad request is redirected to the number two, and so on.
Daisy chains are used for renmant inventory or small website inventory.
For a website with international audience, it is possible to have several daisy chains according to visitor location as ad networks may have different offered prices according to countries.