Here is a table of equivalent concepts in Active Directory vs in Azure AD (or shall we say, Entra ID).
| Windows Server AD | Azure AD Equivalent |
|---|---|
| LDAP | REST APIs |
| NTLM | OAuth/SAML |
| Kerberos | OpenID |
| OU Tree | Flat Structure |
| Domains / Forests | Tenants |
| Trusts | Guests |