Here is the explanation from ESPN:
The six games will include three “contract bowls” and three “host bowls.” The spots in the contract bowls are reserved for teams that have deals with those bowls.
The contract bowls are: Rose (Pac-12 versus Big Ten), Sugar (SEC versus Big 12) and Orange (ACC versus Big Ten, SEC or Notre Dame).
While a Big Ten or SEC team could be selected to the Orange Bowl, the commissioners have agreed that when the Rose and/or Sugar bowls are hosting the semifinals, the Big Ten or SEC champion will not be placed in the Orange Bowl. Instead, it would have to be placed in one of the three other access bowls to increase the worth of that bowl, sources told ESPN.
Those remaining three access or “host” bowls still must be determined, but the leading candidates are the Fiesta, Cotton and Chick-fil-A, sources said.
With the “Group of Five” earning an automatic bid, that will lock up seven of the 12 berths in the six access bowls. The other five berths will be filled with at-large teams chosen, based on their final rankings, by a yet-to-be-formed selection committee.
What does this mean for UMass football? Well, it means that a move to the Big East is now at the very least much closer to a parallel move than a “move up” from the MAC.