Performance Monitor is a built-in tool in the Windows operating system that helps users track the performance of their computer. It provides real-time data on various system metrics, such as CPU usage, memory consumption, disk activity, and network performance. This information can help users identify potential issues and optimize their system's efficiency. Users can customize Performance Monitor by adding specific counters to monitor particular aspects of their system. It also allows for the creation of data logs and alerts, enabling users to analyze performance trends over time. This tool is especially useful for system administrators and advanced users looking to maintain optimal performance.