Notification Rules: What Actions (or lack thereof) Meet the Response Due By and Due Date Triggers?

I see that there are 2 fields : $DueResponseTime and $DueByDate.

Please confirm my understanding the $DueByDate is the date established by the priority level and associated SLA that we expect resolution or service to be complete and the ticket closed
However, what is the DueResponseTime? What constitues a response so that this notification rule is not triggered?
Finally - the "Request Unpicked By A Group" - pleaese confirm this means when ticket assignment to a technician in that group is not made by a certain period of time, the Support Group setting to "Send notification to technician(s) when a request in this group is left unpicked." will send a notification based on the time set.

I apologize but the SDP Manual is not very informative on these settings and triggers. The manual is also not updated for the Release 9 of the application.