A review paper is the one that simply appraises already published articles. It does not contain any primary research.
An empirical study is that which has statistical research in the form of the primary.
Many would not know that the lack of a well-defined theoretical framework can be an important reason for the failure of research. A research study aims to explore the unexplored or under-explored aspects of a subject.
The rationale is written to describe the reasons for any study or research. It proffers a problem with apt solutions. It is a vital portion of any research as it explains the novelty and significance.