The purpose of an application performance monitoring tool is to track and analyze the performance of software applications to ensure they operate optimally. These tools provide insights into response times, server health, and user interactions, highlighting potential bottlenecks or issues that could affect user experience. By gathering performance metrics, application performance monitoring tools allow developers and IT teams to identify and resolve issues proactively before they become critical. They are vital for maintaining high levels of availability, enhancing user satisfaction, and optimizing resource usage in production environments, thus supporting overall application reliability.