Its easy to get confused between OAuth and SAML and how they differ when talking about SSO protocols. I found a great, simplified breakdown online by a reddit user.
"SSO - the experience of logging in one place and being automatically logged in somewhere else
Federation - authenticating from one system to another automatically
OAuth2 - a specification to implement delegation / authorization
OIDC - a spec built on top of OAuth2 that supports authentication and let’s you use a JSON / JWT / id_token as a way to pass info about the authenticated user
SAML - a spec that supports authentication and let’s you use XML / SAML to pass info about the authenticated user
So TLDR - SAML and OIDC are two means to implement federation which in turn is a way to implement SSO between two systems."
Its easier to remember that OAuth2 & OIDC go together (Authorization & Authentication and SAML is an older technology that only performs authentication.