Identity federation is a process where different systems are linked together so users can access these systems using a single set of credentials. This allows users to access multiple services without needing to log in repeatedly, streamlines the login process, and reduces management overhead for organizations. Identity delegation, on the other hand, refers to the practice where one system acts on behalf of another, typically in relation to authorization. It enables fine-grained control over what a third-party can do and is ideal when users need to allow external applications to access specific resources without sharing sensitive credentials. Both concepts serve different purposes and are typically used in complementary ways, with identity federation focusing on authentication and delegation focusing on permissions. Understanding the nuances of these two concepts puts engineering teams in a stronger position to build robust systems that meet the evolving demands of modern environments.