An air ticket consolidator is a travel agency that has contracted with one or more airlines to distribute discount tickets. They can afford a lower price because they pay wholesale prices for blocks of tickets that are likely not to be sold out otherwise. Or they rebate their commissions from the airlines. Particularly on international flights, consolidator fares are generally the best discounted air fares available.
Some ticket consolidators sell only wholesale to travel agents that retail the tickets; some sell directly to the public, and some do both. You can find their ads for reduced prices in the travel sections of big-city papers around the country. Many top airlines sell tickets through discounters.
Ticket consolidator (wholesaler, "bucket shop'') is often 30-40% cheaper than buying direct from the airline. They buy blocks of unsold seats from the airlines and resell them at a slim margin. Such tickets are usually heavily restricted and are for a standard profile (e.g., no special meals, no changes, no transfers, no refunds).  It used to be the case that you couldn't get frequent flyer miles for travel on consolidator tickets, but that seems to be changing.  Cancellation penalties are often much more severe than on regular tickets.  The greater the distance traveled, the greater the chances of saving money through a consolidator ticket. This is especially true for international flights. If you're planning a round-the-world trip, definitely use a consolidator to buy your tickets. Ticket consolidator doesn't buy tickets until a month or two before the flight, so you probably won't be able to buy your tickets very far in advance.
If you want to take advantage of low fares, and if frequent-flier benefits are important to you, you may find some helpful information  about how a ticket consolidator operates.
Some consolidators contract with an airline to buy tickets at a "net" rate for each route - a bargain price that remains fixed even if the airline's advertised fares change; then, they add their own markup. These tickets won't usually include price information, and they usually don't earn frequent-flier mileage credit. Nor can you use frequent-flier mileage to upgrade them. In fact, airlines' advertised fares may drop to less the consolidators' best net prices in a fare war.
Other consolidators negotiate extra-large commissions (perhaps up to 40 percent), called "overrides" with one or more lines. When they resell, they retain only a small part of that commission. They pass the rest along to the retail agent or the customer. Prices of these tickets fluctuate along with changes in the published fares. These tickets usually do show the airline's advertised fare in the "fare" box no matter what you pay for the ticket. These tickets may earn frequent-flier mileage and can be upgraded by using a frequent-flier award.
Money savings  is, of course, the biggest advantage of using a ticket consolidator. However, another is that when your travel requirements are last-minute or when airline supersaver fares have already sold out, you still may be able to find low-priced tickets through a consolidator. But you should still book as early as possible, particularly for the peak season.