When you create a repository, you can choose to make the repository public or private. If you're creating the repository in an organization, you can also choose to make the repository internal.
If your GitHub Enterprise Server instance is not in private mode or behind a firewall, public repositories are accessible to everyone on the internet. Otherwise, public repositories are available to everyone using your GitHub Enterprise Server instance, including outside collaborators. Private repositories are only accessible to you, people you explicitly share access with, and, for organization repositories, certain organization members. Internal repositories are accessible to enterprise members. For more information, see "About internal repositories."
Organization owners always have access to every repository created in an organization. For more information, see "Repository permission levels for an organization."
People with admin permissions for a repository can change an existing repository's visibility. For more information, see "Setting repository visibility."
Note: Internal repositories are available with GitHub Enterprise Cloud and GitHub Enterprise Server 2.20+. For more information, see "GitHub's products."
You can use internal repositories to practice "innersource" within your enterprise. Members of your enterprise can collaborate using open source methodologies without sharing proprietary information publicly, even with private mode disabled. For more information on innersource, see GitHub's whitepaper "An introduction to innersource."
All enterprise members have read permissions to the internal repository, but internal repositories are not visible to people who are not members of an organization, including outside collaborators on organization repositories. For more information, see "Repository permission levels for an organization."
If a user is removed from all organizations owned by the enterprise, that user's forks of internal repositories are removed automatically.