From Science Europe Data Glossary
Definition: a data journal is a scholarly journal, usually published online under an open access license, consisting of papers with descriptions of scientifically valuable data sets (data papers).
Explanation: contrary to articles in “normal” scholarly journals, which focus on answering particular research questions, a data paper focuses on aspects of the data used in research: how the data was collected, managed, processed, analyzed, etc. The purpose is both to make the research data better visible, accessible, usable and referable by providing more extensive and attractive descriptions than in the usual cataloguing metadata and to give the data creator credit for the work on the data. Moreover, it provides an outlet for “negative” research results, which are usually not selected for publication in normal science journals.
See also: data paper; data publication