What is the difference between observability and monitoring?

Answer

Monitoring is collecting and alerting on predefined metrics and checks—it answers known questions like 'is CPU above 90%?' Observability is the broader property of being able to understand a system's internal state from its external outputs, so you can investigate problems you did not anticipate. Monitoring tells you that something is wrong; observability helps you ask new questions and discover why. In practice observability builds on rich telemetry—metrics, logs, and traces—while monitoring is one consumer of that data.