Git can be used as a standalone, or in a variety of web services on premises, as well as online. The most popular ones, such as GitHub, GitLab, or Bitbucket, offer additional features. Bitbucket perfectly integrates into other Atlassian products, such as the popular JIRA issue tracking, and provides free private repositories. GitHub lets you host your project website for free, using GitHub pages and more:

While the previous screenshot shows a private repository on BitBucket, the following screenshot shows a public repository on GitHub. You may notice that there are many similarities in the UI. After all, both portals provide access to hosted Git repositories:

Which provider to use is ultimately your choice. Whether your Git repository lives in VSTS or on GitHub does not really matter. The workflows remain the same when committing code, branching, and merging.