This document introduces Crew Resource Management (CRM) and Threat and Error Management (TEM) in aviation, tracing the evolution of CRM from early, sometimes poorly received psychological or management-focused training to a broader scope incorporating concepts like situation awareness. The introduction of TEM in the 1990s provided a framework for proactively identifying and mitigating threats and managing errors, drawing on accident theory. It emphasizes that threats and errors are inevitable but must be effectively handled to prevent undesired aircraft states. The relationship between CRM and TEM is explored, highlighting how CRM behaviors act as countermeasures to errors at various levels, from avoidance to mitigation.