What is a crash dumped / crash minidump?

Windows automatically generates a minidump whenever a program throws an unhandled exception: https://msdn.microsoft.com/ru-ru/library/windows/desktop/ee416349%28v=vs.85%29.aspx

You can open these minidumps with a program like WinDbg to get an idea what caused the exception:

We tried to find the reason for the exceptions when QGIS crashed quite often. Even with our paid QGIS-Support we could not find the reasons for the QGIS-crashes and were told that the minidumps are not necessarily helpful.

A better way for us was to use the QGIS-rel-dev version which writes debug-outputs and listen to these debug-outputs with a program like DebugView (https://technet.microsoft.com/en-us/sysinternals/debugview.aspx ):

If you install qgis-rel-dev with the OsGeo4W-Installer you can start this QGIS-version with the qgis-rel-devXXX.bat file:

In the about-dialog of QGIS you can see if your QGIS-version writes debug outputs:

If you start DebugView and work with QGIS until it crashes you should see what tools / functions were involved when the crash happened: