This dialog is opened with 
Open file(s) with password toolbar action and using with password action on each side of the Home tab. Also, if we are opening any previously loaded DB using the Recent databases panel on the Home tab, and that DB was loaded previously without Save passwords - this dialog will be opened to enter the password again.
Use the same security type and credentials for both projects - use this option to compare database having the same protection options. In this case only Right project field will be active for the right side, all other options will be used from the left side.
Display passwords shows all password texts.
Save passwords (to reopen from recent DB list without password request) as mentioned simplifies work with recent databases, however please note that encrypted passwords are saved on your computer in the application settings file.
If you often connect to the same databases, you can save these connection options to *.acdms files as suggested on this dialog using Save action for each side. Please note that if Encrypt passwords is not selected then passwords are saved as a plain text, so you should save these files to the safe location. These files can be opened directly from the main application window using 
Open file(s) toolbar action or using command line arguments.
