A project post-mortem is a process, usually performed at the conclusion of a project, to determine and analyze elements of the project that were successful or unsuccessful. Project post-mortems are intended to inform process improvements which mitigate future risks and to promote iterative best practices. Post-mortems are often considered a key component of, and ongoing precursor to, effective risk management. 
Elements of a project post-mortem
Post-mortems can encompass both quantitative data and qualitative data. Quantitative data include the variance between the hours estimated for a project and the actual hours incurred. Qualitative data will often include stakeholder satisfaction, end-user satisfaction, team satisfaction, potential reusability and perceived quality of end-deliverables.
Role of time tracking
Successful analysis of project estimate variance is dependent on accurate time tracking. The greater the granularity with which time is tracked, the more detailed an analysis can be performed during the project post-mortem.