Predatory publishing refers to the practice whereby dubious publishers publish scientific works, sometimes for very high fees, without providing quality controls, scientific standards or appropriate publishing services.
Predatory publishing is problematic for several reasons. For example, there is often a lack of careful quality control in the review process. The uncertain long-term availability of published papers also poses a risk, and the reputation of the authors can be damaged. Other problematic phenomena in scientific communication include fake conferences (predatory conferences), paper mills that offer prefabricated manuscripts for sale and falsified metrics.
Are you unsure about the trustworthiness of a publication or source?
Are you interested in the details? Two library blog posts are dedicated to this phenomenon.