After submitting a manuscript to some journals, they ask you to suggest reviewers for your paper.
It is recommended to do this because the editorial team may not find a suitable reviewer for your article so the reviewing process will take long. Do this even for journals that do not require it.
Recommend some suitable reviewers by sending an email to the editor. The important point is that the people you introduce must be well-known and from the developed countries (such as Canada, America, Australia, etc.). Do not suggest your college professors or people from your country or even people from the developing countries. In the meantime, if you do not introduce a reviewer to a journal, they might refer your article to reviewers who are not experts in your field, and experience shows that they reject your article due to minor errors such as incorrect formatting or language errors because they do not want to damage their credibility by accepting a suspicious article (in their view).