Performance testing with JMeter provides an introduction to key concepts and how to implement performance tests using JMeter. Some important steps include designing test plans, preparing the environment, determining metrics and goals, notifying stakeholders, and using JMeter elements like thread groups, samplers, listeners, assertions and configuration elements to simulate load and measure performance. JMeter is an open source tool that can run in GUI or non-GUI mode for load testing web applications and determining maximum operating capacity and bottlenecks under heavy loads.