What does the “Register Supported Filetypes on Startup” checkbox do in the Windows build of foobar2000?

If installing foobar2000 onto a Windows machine, from within Preferences/Shell Integration there’s a link that directs you to the Control Panel, from where the filetypes that will be opened by foobar can be set. In the same dialog, however, there’s also a checkbox labeled “Register supported filetypes”. Could somebody explain what this checkbox does – how is it different from manually specifying which files foobar will open from within the same dialog?