Bitbucket is a web-based version control repository hosting service owned by Atlassian, for source code and development projects that use either Mercurial (since launch) or Git (since October 2011) revision control systems. It offers both commercial plans and free accounts. It offers free accounts with an unlimited number of private repositories (which can have up to five users in the case of free accounts). Bitbucket allows developers to store their source code, track changes, and collaborate with other developers on code projects. It also provides issue tracking, wiki and pull request features. With Bitbucket, developers can easily create new repositories, connect them to existing projects, and manage access rights to the repositories. Bitbucket also provides an easy way to share code with other developers, and a wide range of integrations with other development tools, such as Slack, Jira, and Trello.
The best open alternative to Bitbucket, not being a Microsoft product is a great advantage. :)