Performance tests in Gatling outlines how to use the Gatling load testing tool to test the performance of web applications. Gatling allows writing simulations in Scala to generate load and analyze results. It uses an asynchronous actor model and handles a high number of concurrent users without blocking. The document discusses setting goals for performance tests, using Gatling's GUI to record and replay tests, analyzing results like response times and errors, and validating responses with assertions in the Scala simulations. Code examples demonstrate configuring requests, storing data in sessions, handling responses, and using loops and conditions to model different user behaviors in tests.