You can require pull requests to pass a set of checks before they can be merged. For example, you can block pull requests that don't pass status checks.
By default, any pull request can be merged at any time, unless the head branch is in conflict with the base branch. But as your project matures and stabilizes, you can choose to enforce restrictions on how a pull request is merged into your repository.
Protected branches ensure that collaborators on your repository cannot make irrevocable changes to branches.
Repository administrators can enable protected branches for limiting branch manipulation.
Required status checks ensure that all required CI tests are passing before collaborators can make changes to a protected branch.
Repository administrators can enforce required status checks before a branch is merged in a pull request or before commits on a local branch can be pushed to the protected remote branch.