Office actions fall into two main categories: final and non-final, and substantive and non-substantive.
Non-final office actions are issued the first time an issue is raised. The applicant has the opportunity to respond and resolve the issues. Final office actions follow a non-final response that the examiner considers insufficient; the options narrow at this stage.
Substantive office actions raise issues with the mark itself; likelihood of confusion, descriptiveness, or other grounds that go to the registrability of the mark. These require legal arguments to overcome. Non-substantive (or procedural) office actions raise formality issues; errors in the application details, missing information, or specimen deficiencies; that are typically straightforward to correct.