1.Public access     GitLab allows you to change your projects' visibility in order be accessed  publicly or internally.     Projects with either of these visibility levels will be listed in the  public access directory (/public under your GitLab instance).  Here is the GitLab.com example. （https://gitlab.com/public）     Internal projects will only be available to authenticated users.

2.Visibility of projects
     2,1Public projects      Public projects can be cloned without any authentication.      They will also be listed on the public access directory (/public).      Any logged in user will have Guest  permissions on the repository.
     2.2 Internal projects      Internal projects can be cloned by any logged in user.      They will also be listed on the public access directory (/public) for logged  in users.      Any logged in user will have Guest permissions  on the repository.
     2.3 How to change project visibility      1）Go to your project's Settings      2）Change "Visibility Level" to either Public, Internal or Private

3.Visibility of groups
     Note:  Starting with GitLab 8.6, the group visibility has changed and can be  configured the same way as projects. In previous versions, a group's page was  always visible to all users.      Like with projects, the visibility of a group can be set to dictate whether  anonymous users, all signed in users, or only explicit group members can view  it. The restriction for visibility levels on the application setting level also  applies to groups, so if that's set to internal, the explore page will be empty  for anonymous users. The group page now has a visibility level icon.
4.Visibility of users     The public page of a user, located at /username, is always visible whether  you are logged in or not.     When visiting the public page of a user, you can only see the projects which  you are privileged to.     If the public level is restricted, user profiles are only visible to logged in users.

5.Restricting the use of public or internal projects     In the Admin area under Settings (/admin/application_settings), you can  restrict the use of visibility levels for users when they create a project or a  snippet:          This is useful to prevent people exposing their repositories to public by accident. The restricted visibility settings do not apply to admin users.