Under the Preferences tab you determine how the Preferences, i.e. all the settings of DVdate will be saved so that you will find them the next time you launch the application. The Preferences of DVdate include what is determined by the options, but also all the other parameters and adjustments that you will have made during use, in the different panels of the application.
If you choose Normal Mode, the preferences will be saved in the Windows registry.
If you select Portable Mode then the preferences will be saved in a file named dvdate.ini, and located in the folder from where you launched DVdate. If you started DVdate with the normal installation process, it will be the folder: C:\Program Files (x86)\DVdate\.
Note however that some Windows configurations practice virtualization and will install the ini file in a folder of the type %LocalAppData%\VirtualStore\Program Files (x86) where %LocalAppData% depends on the current user. For example on my system it is C:\Users\Paul\AppData\Local\ when my username is Paul. This is transparent for the operation of DVdate and will only affect you if you want to recover this ini file to modify it manually, which only experienced users should do.
If you choose Do not save when quit, then no record of DVdate preferences will be kept either in the registry or in the file folder. All previous records will be deleted. In this case, when you exit DVdate, you will be asked to confirm that you do not want to save the preferences.