Retaining Selected documents while switching views...
If you select documents in one view and hold the Ctrl+Shift keys down, while selecting another view, your documents will remain selected. Otherwise, your selections are all automatically de-selected.
Where this might be helpful:
With View Show Selected Only (toggle) you can troubleshoot documents appearing in some views but not in others. Or, you want to select documents based upon a certain sort order/category that appears in one view, but then switch to another view and select others based upon some other sort.