Power systems operation is the academic and practical discipline concerned with the real-time management, control, and optimization of electrical power grids. It investigates the complex dynamic behaviors, stability, reliability, security, and economic efficiency of interconnected generation, transmission, and distribution systems under varying conditions. Key characteristics include the development and application of advanced analytical techniques, control strategies, and computational tools to ensure continuous and resilient electricity supply, particularly in the context of integrating distributed and variable energy resources. Its significance lies in enabling the safe, reliable, economic, and sustainable functioning of the critical infrastructure that powers modern society.