This refers to both journals and publishers that exist purely to make money, not to advance knowledge or the spread of accurate, peer-reviewed information. The term was coined by Jeffrey Beall, a former librarian at the Auraria Library, University of Denver, who has done a large amount of scholarship and advocacy on the issue, including starting Beall's List an online resource that lists suspected and confirmed predatory publishers. With the growth in online publishers and the open access movement, the term has grown since its inception. The following are also considered predatory:
Predatory publishers often solicit submissions through emails, so be wary of Call For Proposals that you receive to institutional accounts or emails you have posted to professional websites, etc. These publishers also tend to target students and early-career professionals, taking advantage of the pressures of "publish or perish" academic culture and lack of experience.