Microsoft Entra ID
Also known as Azure AD, Azure Active Directory
Microsoft's cloud identity service, the account directory behind Microsoft 365 and thousands of connected applications.
Renamed from Azure Active Directory, it is where your users, groups, devices, and application registrations live, and where sign-in policy is enforced. Despite the shared name it is not the same product as on-premises Active Directory and works quite differently.
For most businesses it is the highest-value security surface in the estate. Conditional access, MFA policy, privileged role assignment, and sign-in logs all live here, which makes it the first place to look during an account compromise.
Where this comes up
Microsoft Entra ID sits inside our identity and access work. If you are trying to work out what this means for your own environment rather than in the abstract, that is the page worth reading next, and a short call will get you a straight answer faster than either.