Force theme - If set to "Do not force" then the default theme (which you see on the front page of Moodle) will be used. Otherwise you can choose from a list of themes.
Force language - we recommend leaving this to "Do not force". This way students can choose their own language from the language drop-down menu in the menu bar.
News items to show - if you are using the "recent news" block, then this determines how many items it will display.
Show gradebook to students - determines whether students can see the Moodle gradebook for their own grades.
Show activity reports - determines whether students can see their own activity reports in the course. Teachers can always see activity reports, no matter what this is set to.
» Guide to Moodle