A repository is like a folder for your project. Your project's repository contains all of your project's files and stores each file's revision history. You can also 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.
For user-owned repositories, you can give other people collaborator access so that they can collaborate on your project. If a repository is owned by an organization, you can give organization members access permissions to collaborate on your repository. For more information, see "Permission levels for a user account repository" and "Repository permission levels for an organization."
Repositories can be public or private. Public repositories are visible to everyone. Only the owner and collaborators can view or contribute to a private repository. For more information, see "Setting repository visibility."
Each person and organization can own unlimited public repositories and invite an unlimited number of collaborators to public repositories. With GitHub Free, you can use unlimited free private repositories with a limited feature set and add up to three other people as repository collaborators. To get unlimited private repositories with unlimited collaborators, you can upgrade to GitHub Pro, GitHub Team, or GitHub Enterprise Cloud. For more information, see "GitHub's products."
You can collaborate on your project with others using your repository's issues, pull requests, and project boards.