Google this month released the feature that allows publishers to set target CPMs on open auction to buyers, advertisers, or brands. This means that publishers can have multiple floor prices on individual queries, either higher or lower than the target CPM that a publisher provides, but across multiple queries, the average CPM for the inventory will be higher than the target CPM.
The feature is only available for publishers connected with Google Ad Exchange. Google recommends publishers to have fewer than 200 rules per rule type (pricing, blocking), as more rules create more ad serving latency.
Until now, publishers could only indicate a floor price (fixed CPM). A floor price means that the lowest winning bid must be no less than the floor price. Floor prices (fixed CPM) is is still available, and Google recommends setting the floor price to $0.00.
With the target CPM, Google adjusts floor prices to match more bids. Google says that publishers switching from floor prices to target CPM should not start with higher CPM than the existing floor price.