For a full walkthrough, please see this overview of OCM.
For every flight you create in Omny's Campaign Manager, you have three priority types to choose from.
Sponsorship has the highest priority and will always beat all other priority options when competing for a slot. No impression goal is set.
‘Standard’ is the middle priority and has a predefined impression goal. Standard will always beat flights with a remnant priority.
Remnant is the lowest priority and has no impression goal. This sort of flight can be used to run house campaigns to ensure that no potential impressions go to waste.
To give you more flexibility, for each priority type you can also weight these with either low, medium or high:
Once impressions have been delivered, the flight 'Type' can't be changed but the 'Priority' setting can. This allows you to 'boost' a campaigns priority slightly to get it delivering more quickly.