Price priority Line item type most commonly used to fill your site's unsold inventory if not contractually obligated to deliver a requested number of impressions. (Learn more about price priority line items in DoubleClick for Publishers) [Term in DART for Publishers] 
Time-based bulk A paying ad that runs only for the time period specified, doesn't have impression goals, and runs at the lowest priority of all paying ads. When a time-based bulk ad is running, no non-paying ad of the same pixel size can run in the ad network. The time-based bulk ad is always served instead of the non-paying ad.