What is Price Floor?
Think of a Price Floor in a similar way to the reserve price for a Real Estate auction. i.e the price that the auction will be passed in if there are not a single bid that exceeds the reserve.
The Price Floor for an impression to be sold programmatically via an online auction is the minimum closing price set by the publisher within their ad server. Price Floors are can be set in the Ad Server in a variety of way such as at the domain level, geography, ad size, placement or at the user level. Every ad server handles Price Floors differently.
Publishers who set their Price Floor too high can face the issue of low fill rates and thus greatly impacting overall yield for the publisher. The best way for publishers to maximize yield is to not set a Price Floor at all and to simply leverage off all the competition within the ad server ie Header Bidding, deals, Direct Campaigns, Open Exchange and Daisy Chain.
It is advantageous for a Advertiser buying programmatically to know the Price Floor for one or many publishers so they can best set the bid prices in their campaigns.