Git and GitHub are not the same thing. Sometimes, for engineers who are new to version-control systems, this is confusing. Git is a revision-control system while GitHub, https://github.com/, is a centralized hosting service for Git repositories. 

Because Git is a decentralized system, GitHub stores a copy of our project's repository, just like any other developer. Often, we just designate the GitHub repository as the project's central repository and all other developers push and pull their changes to and from that repository. 

GitHub takes this idea of being the centralized repository in a distributed system further by using the fork and pull requests mechanisms. For projects hosted on GitHub, encourage developers to fork the repository, or make a copy of the repository, and work on that copy as their centralized repository. After making changes, they can send a pull request to the main project, and the project maintainers can review the changes and commit the changes if they see fit. GitHub also adds the web interface to the repositories besides command line; this makes Git more user-friendly.