Research is a systematic process of inquiry that contributes to the advancement of knowledge, understanding of phenomena, and resolution of real-world problems. This chapter explores three major types of research: Fundamental Research, Applied Research, and Action Research, highlighting their distinctive characteristics, objectives, applications, strengths, and limitations. Fundamental research focuses on expanding theoretical knowledge and developing new concepts, whereas applied research emphasizes the practical application of scientific knowledge to address specific societal, technological, educational, and industrial challenges. Action research, on the other hand, adopts a participatory and cyclical approach involving problem identification, planning, implementation, observation, evaluation, and reflection to improve practices within specific contexts. The chapter also examines the interrelationship among these research approaches and explains how they complement one another in generating knowledge and promoting practical innovations. Furthermore, it discusses the significance of selecting an appropriate research approach according to research objectives, available resources, and the nature of the problem. The discussion highlights that the integration of fundamental, applied, and action research can strengthen scientific inquiry, encourage innovation, and facilitate sustainable improvements in different fields of human activity.