k6 is an open-source load testing tool used to perform performance and load testing for web applications and APIs. It allows developers and testers to simulate high user loads and analyze the system's performance under various scenarios. With k6, you can write test scripts in JavaScript to define user scenarios, set virtual user behavior, and analyze the performance metrics and results. k6 provides features like distributed load testing, scripting flexibility, metrics visualization, and integration with CI/CD pipelines. It is designed to be developer-friendly and scalable, making it a popular choice for load testing and performance testing of web applications and APIs.