Absolutely fair--there are a lot of defined terms earlier in the book that would help to have seen, and even then it really only made sense to me putting it into play the first time. Basic rundown, though there are others in the room who can probably correct/clarify any/all of this:
A front is a setting/narrative structure: it's a description of an entity, its goal, the resources it has to pursue that goal, the doom that will befall the adventurers/world if that goal is met, and the harbingers of progress toward that goal. The entity could be a villain, a faction, an impersonal force....