Import Settings are the settings used for quick import. You can enable quick import in the Import or by un-checking the Always Show Import dialog when importing... option for the type.
Filetype - Select a file type to determine the settings for that specific type
Always Show Import dialog when importing XX files - when enabled all Import methods will show the import dialog.
Settings - The Settings will vary depending on which filetype you have selected. See the Import page for detailed descriptions of all the settings