This lesson focuses on understanding the terminology used in professional standards for audit and non-audit engagements. Key terms discussed include "should," "may," "might," and "must," each of which has distinct implications for the level of obligation an auditor has when following prescribed guidelines. The concept of reasonable assurance is also explored, emphasizing that while auditors strive to provide a high level of confidence in detecting material misstatements, they cannot guarantee absolute assurance due to the inherent limitations of the auditing process. By gaining a solid grasp of these terms, one can better comprehend the expectations and requirements placed on auditors in various situations.