Summary
A repository contains all of your project's files and each file's revision history. You can discuss and manage your project's work within the repository.
You can own repositories individually, or you can share ownership of repositories with other people in an organization.
About repositories - GitHub Docs
github.com
Summary
GitHub allows users to choose a repository's visibility when creating one, allowing them to be public, private, or private. Organization owners always have access to every repository created in an organization, and people with admin permissions can change an existing repository's visibility. Internal repositories are accessible to enterprise members, and if a user is removed from all organizations owned by the enterprise, their forks of internal repositories are removed automatically.
About repository visibility - GitHub Docs
github.com
Summary
Internal repositories are available in GitHub Enterprise Server 2.20+. 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.
Migrating to internal repositories - GitHub Enterprise Server 3.1 Docs
github.com
You can choose who can view your repository. ... Note: Internal repositories are available with GitHub Enterprise Cloud and GitHub Enterprise Server 2.20+. For ...
Setting repository visibility - GitHub Docs
github.com