In social and behavioral sciences databases you will find different kinds of research articles.
Original Research Studies
The first type of article is the original research study. Original research studies report findings interesting to a particular research area or field. Researchers will report the methods and theories researcher used to arrive at those findings, including limitations the researcher experiences.
The second type of article is a review article. Review articles selectively reviews important studies, methods, and theories, relevant to particular research area or discipline. There is also a kind of review article, called a meta-analysis, which analyzes the effectiveness of statistical measures in particular research area or sub-discipline. Systematic reviews are very popular in the health and medical sciences. These kinds of review articles tell you exactly what kinds of literature and databases were searched in great detail (including defining the search parameters and the types of keywords used).
Book reviews are also popular in research journals. And you can find experts reviewing monographs, chapter by chapter, with great attention to how the book connects to the current literature in particular research area.
Editorials are also included in research journals. These are opinions of prominent researchers, in a particular subfield. They usually comment on a the theme of particular journal issue, or call attention to a topic that the author of the editorial has strong opinion about (future direction of a field of inquiry, appropriate research methodology, etc.).