Predatory publishers usually request payment for publishing, and usually in advance of accepting the article. Some predatory practices include (but are not limited to): may not include peer-review, may not have a legitimate editorial board, and may not publish high quality papers. See more on the Avoid Predatory Journals tab in this guide.
Legitimate publishers may charge an Article Processing Charge (APC) if you want your article to be available open access. The open access APC option will only be available after your paper has been accepted.
With gold open access journals, all articles are open access, but not all will charge an APC. Hybrid open access journals offer the option for open access, but the APC is usually a lot higher, and the journal itself is behind a paywall. More about APCs.
NOTE: Just because a journal is Open Access does not mean it is predatory. Learn more on our Open Access guide.