a SkyVault site is a area where you can share content and collaborate with other site
      members.
    Any user can create a site. The site creator becomes the Site Manager by default, though additional or alternate managers can be added after this.
Each site has a visibility setting that marks the site as public, moderated, or private. This setting controls who can see the site and how users become site members.
- Public site
 - All users can view the content but only site members can work with the content.
 - Any user can join the site.
 - Moderated site
 - All users can access the site but only site members can see and work with the content.
 - Users must ask to join the site.
 - Private site
 - Only site members can access the site.
 - Users must be added to the site by a site manager.
 
The manager of any site—whether public or private—can add users.
Note: The visibility setting of a site is displayed next to the site name when you're in the
      site. 
    You can remove yourself from a site at any time by clicking 
 in the site and selecting
        Leave Site.