Requirements are tests that the PR needs to pass, in addition to the approval of reviewers. If any of the requirements fail, so does the PR.
Currently the only configurable requirement is
If the PR contains modifications to .pullapprove.yml, you will also see that show up as a requirement, with the requirement being that the proposed .pullapprove.yml is in fact valid. The benefit of this is that assuming .pullapprove.yml is modified through a PR, you will get a built-in check to help ensure that an invalid configuration is not put in place.