What does the study type mean?
There are many study types in clinical research divided within two broad categories: interventional and observational studies.
Interventional studies (also called experimental) are studies in which volunteers receive one or more interventions so that the researchers can evaluate the effects and define the outcomes.
Observational studies (also called epidemiologic) are studies in which the investigator (a doctor/researcher) is not acting upon study participants, but instead observing natural relationships between factors and outcomes.