AAR (After Action Review) is a method of capturing and sharing practical knowledge from the field used by the U.S. Army. The core of the method is that after hostilities, a commanding officer prepares a report evaluating the action (After Action Review).
Transposed into the environment of the organization, this means that after completing the task or project, the leader of the task, i.e. the project manager and all key team members should prepare a short report on the essential characteristics of all completed activities and highlight anything new which they have learned while completing the task. Reports are preferably stored in an electronic information system (intranet, wiki, etc.) to make them available to all employees of the organization to whom they may be relevant.