Generally (though not always), you will be approached by a predatory publisher or journal. If an invitation to submit feels dodgy or too good to be true, it probably is. But even if it doesn't seem odd, it is always important to check out any publisher or journal before you submit to them.
What are predatory journals or publishers? "Predatory journals and publishers are entities that prioritize self-interest at the expense of scholarship and are characterized by false or misleading information, deviation from best editorial and publication practices, a lack of transparency, and/or the use of aggressive and indiscriminate solicitation practices".
Grudniewicz, A., Moher, D., Cobey, K. D., Bryson, G. L., Cukier, S., Allen, K., ... & Ciro, J. B. (2019). Predatory journals: no definition, no defence. Science (576)7786. 210-212.
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