What is Lessons Learned?

Lessons learned is the discipline of capturing what worked and what didn't — throughout the project, not just at closure — and registering it where future projects will actually find it. It's organizational memory made deliberate.

The exam expects continuous capture (the register is updated all project long) and closure-time consolidation into the organization's repository. A team repeating a sister project's known mistake is the classic symptom of lessons documented but never consulted.