The paper covers the basic architecture of linear and switching mode regulators, block diagram level descriptions of the PMU, the important electrical parameters for PMU characterization, characterization methodology, instruments used for characterization, some best practices for characterization in terms of the board guidelines, test points, and debugging the issues. This will help any characterization novice trying to understand post-Si characterization and hobby readers, especially undergraduate college students, looking to make a career in Post-Si characterization.