You can set up required status checks to either be "loose" or "strict." The type of required status check you choose determines whether your branch is required to be up to date with the base branch before merging.

Type of required status check Setting Merge requirements Considerations
Strict The Require branches to be up-to-date before merging checkbox is checked. The branch must be up to date with the base branch before merging. This is the default behavior for required status checks. More builds may be required, as you'll need to bring the head branch up to date after other collaborators merge pull requests to the protected base branch.
Loose The Require branches to be up-to-date before merging checkbox is not checked. The branch does not have to be up to date with the base branch before merging. You'll have fewer required builds, as you won't need to bring the head branch up to date after other collaborators merge pull requests. Status checks may fail after you merge your branch if there are incompatible changes with the base branch.
Disabled The Require status checks to pass before merging checkbox is not checked. The branch has no merge restrictions. If required status checks aren't enabled, collaborators can merge the branch at any time, regardless of whether it is up to date with the base branch. This increases the possibility of incompatible changes.

Further reading