A thermal concentrator is a thermal functional device based on transformation thermotics, effective-medium theory, and scattering-cancellation principles. By tailoring the spatial distribution of thermal conductivity or geometric configurations, it efficiently concentrates large-scale heat flux into localized regions, enabling precise control of both steady-state and transient heat transport. With advances in materials science and manufacturing technologies, research on the thermal concentrator is moving from theoretical models toward engineering implementation, and it shows application potential in microelectronic cooling, thermoelectric energy harvesting, energy heating, and thermal therapy. This article systematically reviews the physical mechanisms, structural designs, and implementation pathways of the thermal concentrator, summarizes its development and representative works, compares the applicability and performance characteristics of different theoretical frameworks and configurations, and analyzes its technical advantages and engineering feasibility in typical application scenarios. Finally, this article discusses future trends of the thermal concentrator, including extensions to complex geometries, multiscale systems, emerging energy platforms, and extreme thermal environments.