The link between the question and understanding is the heuristic structure. Heuristic structure is intricately linked to the anticipation of understanding one spontaneously experiences when one inquires. Thus, moving intelligently from question to insight is what Lonergan means by heuristic. The moving or development follows a road that is not designated. It is a road that gives one signs but not directions.
Heuristic structures carry no content.
The criteria of heuristic structures are satisfied when the form they anticipate is filled. Understanding fills that form. Heuristic structure is detached from the actual content of that understanding. It has no substance, it is merely an orientation toward an unknown. It allows you to name the unknown.