This blog post explains observability, a method to understand how a system works by examining its outputs. Observability is different from monitoring, which just collects data. The three pillars of observability are metrics (numerical indicators), logs (event records), and traces (request flow tracking). Popular observability tools include Prometheus, Grafana, Jaeger, ELK Stack, Honeycomb, Datadog, New Relic, Sysdig, and Zipkin. By understanding these pillars and using the right tools, you can gain valuable insights into your system's health and troubleshoot problems before they impact users.