Statuses let you know if your commits meet the conditions set for the repository you're contributing to.
Statuses are based on external processes, such as continuous integration builds, which run for each commit you make. You can see the pending, passing, or failing statuses for each commit in your pull request.
You can see the overall status of the last commit to a branch on your repository's branches page or in your repository's list of pull requests.
Organization owners and users with push access to a repository can create statuses with GitHub's API.