System mapping is a technique to visualize and communicate the complexity of systems. It can be used to map dependencies, workflows, and other relationships. The process involves talking to people to understand the system, capturing information, getting feedback, and iterating. Graphviz is one open source tool that can be used to generate visual maps from code. System mapping helps build shared understanding, discover issues, and extract implicit knowledge about the system. It works best when curated over time and can reveal unexpected connections and risks.