What Is An Agency Consortium?

A consortium is a group of agencies that have banded together to enable their combined sales power to negotiate better deals for their clients.
The cruise lines know that this consortium has many choices for "preferred suppliers". For example they know that the consortium members have lots of options for Alaska cruises -- Princess , Holland America, Royal Caribbean, and Celebrity are all big players. The consortium can go to all of these cruise lines and ask what the cruise line is willing to offer to be a preferred supplier for Alaska cruises for next year.
In return for additional advertising and promotions the cruise line might offer exclusive fares, shipboard credits, complimentary upgrades, or other amenities to clients of any of the consortium's agencies. So a client that books her cruise through one of the consortium's agencies can get a great deal that's not available elsewhere.
There are many consortia out there. Signature Travel Network, Virtuoso, Ensemble, Vacation.com are some of the largest and some of the travel agency franchises can offer similar deals -- Cruise Planners, Cruise Holidays, CruiseOne, Travel Planners, and Expedia Cruise Ship Centers are some that are available. Like a consortium, the franchise members will combine their selling power to negotiate extra benefits for their clients.
Not all agencies/consortia are the same. For example, some might feature Avalon River Cruises as a preferred supplier and offer extra benefits while members of another consortium may not be able to offer you anything extra because Avalon is not one of their preferred suppliers. The agency that's the best choice for a Royal Caribbean cruise might not be able to get you anything extra on an Oceania cruise and vice versa. And the consortium might block group space on hundreds of a preferred cruise line's sailings making group space available through any of their member agencies.