Identity and Access Management (IAM) is the security discipline that ensures the right individuals access the right resources at the right time for the right reasons. It sits at the intersection of cybersecurity, directory services, authentication protocols, and compliance frameworks, functioning as the gatekeeper between users, applications, and sensitive data. Unlike perimeter-based security models that trust everything inside a network, modern IAM operates on continuous verification, dynamic policy enforcement, and fine-grained access control. The key mental model: identity is the new perimeter—every access decision depends on proving who (or what) is requesting access, what they're allowed to do, and whether the context justifies the request.