Retrospective plays a significant role in any of the Agile frameworks. One of the Twelve Principles published with Agile Manifesto says:
At regular intervals, the team reflects on how to become more effective, then tunes and adjusts its behaviour accordingly.
Retrospective enables the Development Team to focus on self-improvement. The basic recipe for this event is quite simple: (1) review what has happened in the last iteration, (2) plan action to improve what can be improved and preserve what if worth to be preserved, (3) try to carry on with this plan in the upcoming iteration.
Things become a bit more complicated when we are in the environment where more than one Development Team are involved (Let’s assume we have three teams or more). Why?
