Github is a powerful service for collaborative development of apps, helping comment, review changes and report issues on project
GitHub - the largest web hosting service for projects and joint development and based on the version control system Git.
In other words:
GitHub - service based system Git, which allows you to organize joint work of several users on the same project - developers can create a project, without disturbing or removing the code of one another. In addition, through the use of a version control system, can achieve a high level of protection from fatal errors during development.
What is it used for?
GitHub is used in all development projects that involve more than one developer.