Flexible alternating current transmission systems (FACTS) deployments and applications are on the increase in modern day power network systems because of their advantages over conventional ways of power network physical expansion. Therefore, a comprehensive review of FACTS controllers with their various applications is carried out in this paper. Formation of different applications and advantages of FACTS devices into voltage control, power flow control, system stability control, power quality control, and economic benefits as inferred from the literatures is among the vantage points of this presentation. FACTS background alongside different techniques of deployments, leading to various applications and performance of these devices, hitherto organized structurally based on target objectives are also explored, presented and discussed. Summarily, this study provides an overview of the background, topological structures, deployment techniques and cutting-edge utilization of FACTS controllers, with a view to acquainting power players, electrical engineers, network designers as well as researchers, with the trends in the development, status and future direction of FACTS applications. Convincingly, the content of this article will benefit all the stakeholders in the area of FACTS deployments and utilizations.