Are you familiar with revision control repository services? GitHub is a well-known Git-focused revision control repository service.
GitHub is a Git revision control repository service. In addition to providing a Git repository, GitHub provides a nifty grapical interface as well as several team collaboration tools, which includes tracking issues, setting milestones, wikis and integration with project management boards(called projects). Forking off repositories, creating pull requests and easy merging make GitHub a good tool for projects and teams.
GitHub provides both cloud-hosted and self-hosted offerings. The cloud-hosted service offers a free service tier as well as paid plans. All self-hosted offerings are paid.