When you add site content in the form of events, articles, jobs, CMS pages, etc., you must check the boxes at the bottom of the page that specificy viewing rights. 

You can allow everyone to view the content (Anonymous), require log in to view (Site User), or require membership (Member) to view the page. 

NEW!
You can also assign viewing rights to a specific User Group by choosing the Group or Groups from the Allow members of the following user group(s) to view this content: field. For example, you could restrict viewing of the proposed budget to just the Executive Board committee by unchecking the view checkboxes listed above and selecting the Executive Board User Group. You can also combine this field with the checkboxes. For example, all organization Members and all members of the Advisory Board User Group can view the page.

The majority of your site will probably be set to allow everyone to view the content. Certain sections however can be restricted, such as requiring job searchers to register with the site or restricting financials to members only. 

How you administer the site is up to you.