This introduction chapter presents a comprehensive overview of vanadium redox flow batteries (VRFBs), a promising technology for large-scale energy storage applications. As the global demand for renewable energy sources continues to rise, the need for efficient and sustainable energy storage solutions becomes increasingly critical. This chapter begins by outlining the fundamental principles of RFB operation, emphasizing the different typologies, applications and existing systems, and the unique characteristics that distinguish VRFBs from conventional battery systems. Furthermore, the importance of accurate modeling and control strategies for VRFBs is discussed, as these factors directly influence system efficiency, operational stability, and longevity. The chapter reviews existing research done, with multiple modeling approaches, including electrochemical, thermal, and dynamic models, highlighting their strengths and limitations. It also addresses the challenges associated with state estimation, particularly the state of charge (SoC) and state of health (SoH), which are crucial for optimizing the performance and lifespan of VRFB systems.