1) short name: o11y

2) idea: like a doctor checking external signals to understand internal issues

3) Twitter pillars: monitoring, alerting/Visualization, Distributed Systems Tracing Infrastructure, Log Aggregation/Analytics

4) telemetry definition: get remotely information from equipment

5) opentelemetry 

• is not a replacement ❌🔃 for your monitoring tools
• is 100% free 🆓 and open source 🔓
• provides you with metrics, distributed traces, and logs 
• is kind of JDBC as it connects to observability collectors

6) Distributed tracing is done with a correlation id

7) In the demo, I saw the outputs in the spring boot logs, then in a GUI done by Zipkin (which looks like the network tab of the chrome dev console with the horizontal bars)