MFA (Multi-Factor Authentication) is a mechanism that requires at least two proofs of identity of different kinds: something you know (password), something you have (phone, security key) or something you are (biometrics).
SSO (Single Sign-On) lets a user sign in once with an identity provider (Microsoft Entra ID, Okta, Google Workspace) and then access every connected application. It relies on protocols such as SAML 2.0 or OpenID Connect.
The two go together: SSO concentrates access in one place, MFA protects that place. Passkeys (the FIDO2 and WebAuthn standards) are gradually replacing passwords and one-time codes with passwordless sign-in that is more resistant to phishing.
Why it matters when hiring
The topic comes up with security, IT and back-end profiles, and in any SaaS selling to large accounts, where SSO is often required. A good developer can integrate SAML or OpenID Connect without rewriting their own authentication. A good IT profile can roll out MFA without blocking teams. Check that they distinguish authentication from authorization.