Performance testing is a type of software testing that evaluates how a system performs under various conditions. It measures factors such as speed, responsiveness, and stability when subjected to different workloads. This helps identify bottlenecks and ensures that the application can handle expected user traffic. The main goal of performance testing is to ensure that a system meets specified performance criteria before it goes live. It can involve different types of tests, including load testing, stress testing, and endurance testing, each focusing on different aspects of performance to ensure a smooth user experience.