Performance testing tools are software applications designed to evaluate how a system behaves under various conditions. They help identify bottlenecks, measure response times, and assess the overall stability of applications. Commonly used in software development, these tools simulate multiple users to ensure that the application can handle expected loads. Examples of popular performance testing tools include Apache JMeter, LoadRunner, and Gatling. These tools provide valuable insights into system performance, allowing developers to optimize their applications before deployment. By using performance testing tools, organizations can enhance user experience and maintain system reliability.