To elaborate/add further to the details shared by Marc:
A list view report displays unsummarized or detailed data as a list.
A summary view report displays summarized data as summary counts, totals, or averages, charts/graphs and you can drill down to supporting information i.e, when the user drills down on a row in the report, you can drill down to another report or chart from the selected row.
Note that the list view rule and the summary view rules are deprecated from pega 7.1.9; although, existing list view reports and summary view reports are still supported.
Reports based on the list view and summary view rules use framesets to provide a view of drill-down reports. HTML5 does not support framesets, so list view and summary view reports might not display well, or at all, in some browsers. To prevent display issues, re-create the custom list view and summary view reports that you need as report definition reports.
You can create list reports and summarized reports by using the report definition rule. Standard management reports are report definition reports.