Observability is about understanding a system's behavior and performance from its external outputs, allowing proactive analysis and optimization of complex systems with distributed teams and microservices. Traditional monitoring can only track known unknowns, whereas observability provides the flexibility to understand patterns and unknown unknowns, enabling proactive issue detection and resolution. Observability has four fundamental pieces: metrics, events, logs, and traces (MELT), and requires open instrumentation, correlation and context analysis, programmability, and AIOps tools to make sense of telemetry data. It enhances customer experience, reduces downtime, improves team efficiency, and fosters innovation, making it a crucial component of modern digital business.