I heard (possibly in the name of the Beer Mayim Chaim) that all of Rashi's commentary al hatorah addresses one of six questions: קושי בדקדוק, סמיכת הענינים, לשון מיותר, סתירה, שינוי בלשון, קושי הבנה
I also found this on chinuch.org
Does anyone have a reliable source for this?
Thank you in advance.