opera:about                   display version # and see the credits.
opera:activity                beta and developer.  lists open tabs in that browser only.
opera:bookmark-importer       imports bookmarks from local file.
opera:bookmarks               view your synced bookmarks.
opera:browserjs               not sure.
opera:config                  same as opera:settings.
opera:downloads               List of files in Opera's download folder.
opera:extensions              extensions management page.
opera:flags                   Allows you to turn on experimental functionality.
opera:gpu                     Video card usage and workarounds that may be used.
opera:histograms              not sure
opera:history                 history.  different layout coming soon.
opera:invalidations           used in Opera Developer.  Seems to have to do with sync.
opera:media-internals         not sure.
opera:net-internals           not sure.
opera:plugins                 lists plugins like pdf viewer, Java, flash, etc.
opera:profiler                not sure.
opera:remote-debug            beta and developer.  not sure.
opera:serviceworker-internals not sure.
opera:settings/startup        allows you to set the start page.
opera:settings                Allows for configuration of the browser.
opera:startpage               goes to whatever you have set up as your start page.
opera:themes                  where available themes can be set.
opera:tracing                 not sure.