Predatory publishers charge exorbitant article processing fees without conducting any editing or peer-review work, often preying on inexperienced or desperate authors. Journals owned by such publishers can either be closed or open access, although the latter is more common.
When you're evaluating a journal- open access or not- to determine if your article is a good fit for the publication, remember to spend some time evaluating the journal/publisher to make sure that the goal of the publication is to share high-quality research which advances scholarship versus solely to make a profit.
(Adapted from Canadian Association of Research Libraries. Unless otherwise expressly stated, this information is licensed under a Creative Commons Attribution License.)