Predatory journals are defined as publishers that exploit the open-access model by charging publication fees without providing proper peer review or editorial oversight. They engage in deceptive practices like not informing authors of fees until after acceptance, spamming scholars to publish or join editorial boards, quickly accepting low-quality papers including hoaxes, and falsely listing scholars as authors or editorial board members without permission. Predatory journals can be identified by checking lists maintained at sites like predatoryjournals.com, which catalog journals based on criteria like exorbitant fees, lack of transparency, and questionable publication practices.