If you are examine a research study from the perspective of its objectives, broadly, a research endeavor can be classified as: descriptive, correlations, explanatory or exploratory.
Descriptive research attempts to describe systematically a situation, problem, phenomenon, service or program or provides information about, say, the living conditions of a community, or describes attitudes towards an issue.
Correlational research study is to discover or establish the existence of a relationship, association, interdependence between two or more aspects o a situation. The studies examine whether there is a relationship between two or more aspects of a situation or phenomenon.Explanatory research attempts to clarify why and how there is a relationship between two aspects of a situation or phenomenon.
Exploratory research carries out the investigation of the possibilities of undertaking a particular research study.