Predatory journals are journals without peer-review that have titles that are deceptively similar to those of existing, highly estimated journals published by e.g. Elsevier or Springer.
The lack of peer-review, impact factors and transparency are typical features of predatory journals and these enable you to discover if a journal you are considering publishing in is a serious one or a predatory one.
More on the consequenses of predatory journals for researchers and for DTU
Below you will find a list of points to consider as well as some tools you can use to validate a journal you are considering publishing in.