Few doubts relating to 60016: Updates to Security Profiles

I have been trying to understand what the results are portraying, and have few questions.

1. While changing the security profiles for existing data roles, there are few line items where only Security Profile Id.New and Security Profile Id.Old values are coming up. On the other hand, for some line items, the attributes Security Profile.HrSecuringObject New, Security Profile.BusinessGroupId New are coming up. Why is this so? What am I missing here?
2. What does the attribute BusinessGroupId capture?

It would be very helpful to get some advice here.

Thank you.