Scrum tales - Part 8 - Sprint retrospective

Although Scrum teams followed guidelines and conducted all necessary meetings at the end of a Sprint, it seems that no one fully grasped the idea behind the Sprint retrospective meeting and its core purpose

What is a Sprint retrospective meeting?
Sprint retrospective meeting is a Scrum team meeting initiated and held by the ScrumMaster at the end of each Sprint. In our strict Scrum implementation, three main questions are asked by the ScrumMaster and answered in cooperation with the entire team:
   1) What worked?
   2) What didn't work?
   3) What will we do differently?

These questions are similar to those asked during the Daily scrum meeting, why do we repeat them at the end of the Sprint?
Questions may look similar but they are referring to completely different aspect of the Sprint - its iterative process and internal team organization
During the Daily scrum meeting the team is focusing on individual goals (PBIs) and tasks in the specific Sprint; during the Sprint retrospective meeting the team should be focused on the process that led to PBIs being successful or not and how to make all future PBIs always successful going forward

If we cannot specify concrete PBIs when answering Sprint retrospective meeting questions, what should we talk about?
   1) What worked?
   Discuss and list all the changes in the internal team organization, Sprint planning and ScrumMaster activities that were different compared to the team's previous Sprint; i.e.:
      a) We dedicated more time to make closer task estimates during the Sprint planning meeting
      b) This time we split PBIs for research and planning, and PBIs for development tasks
      c) We identified only the most critical ad-hoc tasks and prioritized them over the Sprint

   2) What didn't work?
   List all the obstacles identified from the moment you started planning the Sprint to the final Daily scrum meeting, especially issues that caused some Sprint deliverables (PBIs) to not be completed on time; i.e.:
      a) We had high risk PBIs that were underestimated at first but we didn't prioritize them in the Sprint
      b) ScrumMaster wasn't persistent enough to unblock externally blocked goals
      c) Our task estimates didn't cover for unexpected team member absences

   3) What will we do differently?
   This is the most important question that you must always discuss and answer even if your previous Sprint has been 100% successful as there is always something you can improve in the process; i.e.:
      a) We will segment tasks better so that more team members can work on the same PBI in parallel
      b) ScrumMaster will review all team blocked tasks daily and act to resolve them even if it means to send a single email follow up every day
      c) We will work with Product owner to define PBIs that are achievable during one Sprint duration vs. moving them across multiple sprints

Is Sprint retrospective meeting the same as Sprint review meeting and can we merge them?
No, they are different meetings. Sprint review is designed for the Scrum team to demo the Sprint deliverables to the Product owner while Sprint retrospective is primarily team-only meeting aimed to adapt and improve the sprinting process within the team and to make all future Sprints 100% successful