Microsoft Active Directory

Active Directory (AD) is Microsoft's umbrella term for various directory-like identity services. Traditional AD is an on-premises solution to manage entities like devices and users on the local network or domain. Organizations can use it as the source of truth for employee entities in the digital space.

Azure Active Directory (Azure AD) is a modern extension of the same concept allowing managing of users and permissions in cloud environments. Most notably support protocols such as SAML, OpenID Connect and OAuth for third-party application integration.

SAML and OIDC are authentication protocols.
OAuth is an authorization protocol.

Azure AD was renamed Microsoft Entra ID in 2023 🤷.