Security Assertion Markup Language - standard for exchanging authentication data between systems. Like having a standardized passport format recognized by all countries.
Enterprise employees use SAML to access both internal company systems and external partner applications with one login.
SAML is a standard, not a single cloud service. These identity services commonly act as a SAML Identity Provider (IdP) or integrate with external IdPs to provide SAML-based single sign-on (SSO) to cloud apps and enterprise SaaS.