For any content that you post, you can decide what groups are able to see it.  While you are editing or creating the content, click on >View/Edit permissions section and you'll see a bunch of roles. For each you get to choose whether that role can view edit or delete your work.

Going from most general (largest audience) to most specific (smallest)....

Anonymous users are people who browse the website but are not logged any - pretty much anyone in the outside world.

Whether it is for pages for a course or research web pages, sometimes you would like to add a collection of related pages. If this is what you are after, Book pages provide automatic heirarchical navagation which holds the pages together as a unit.  I've used this to create the undergraduate and graduate program pages, as well as course pages.  If you want a single page, then a page or a story maybe more appropriate.

Here is how to assemble a book...