The SAML (Security Assertion Markup Language) protocol is an open standard that enables secure, federated Single Sign-On (SSO) between an Identity Provider (IdP) and a Service Provider (SP), allowing users to authenticate once and access multiple applications without re-entering credentials. Through the exchange of digitally signed XML-based SAML assertions, the IdP verifies user identity and securely shares this information with the SP, enhancing both security and user convenience by centralizing authentication and reducing the need for repeated logins.