Azure Active Directory (now called Microsoft Entra ID) is Microsoft’s cloud- based identity and access management (IAM) service that lets users securely sign in and access apps and resources from anywhere.

What is Azure Active Directory?

Azure Active Directory is a cloud directory and identity platform that stores users, groups, and applications, and controls who can access what.

It handles both authentication (signing in) and authorization (what you’re allowed to do) for resources such as Microsoft 365, SaaS apps, and even some on‑premises apps.

In simple terms, you can think of it as the “identity backbone” of Microsoft’s cloud, connecting people, devices, and apps securely over the internet.

Key responsibilities

Azure AD focuses on a few big jobs:

  • Verifying who you are (authentication), e.g., when you log into Microsoft 365.
  • Controlling what you can access (authorization) across internal and external apps.
  • Providing single sign-on (SSO) so one login works for many applications.
  • Enforcing security policies like multifactor authentication and Conditional Access.
  • Managing identities for employees, partners (B2B), and customers (B2C).

Core building blocks

At its core, Azure AD is built around a few main object types inside a tenant (an isolated instance representing your organization).

  • Users: Individual accounts for people or services.
  • Groups: Collections of users that share similar access needs, used to assign permissions at scale.
  • Applications: Registered apps that rely on Azure AD for sign‑in and tokens.
  • Roles: Admin and custom roles that define who can manage what in the directory.

A tenant can be linked to one or more Azure subscriptions, but the tenant itself is the central identity store.

How Azure AD works (high level)

When an organization signs up for Azure or Microsoft 365, a default directory (tenant) is created automatically.

Users and groups are created in that directory; admins then assign apps and permissions to those identities.

When a user signs in:

  1. The user authenticates with Azure AD (often using modern protocols like OAuth 2.0, SAML, or OpenID Connect).
  1. Azure AD issues tokens that apps use to verify identity and permissions.
  2. Conditional Access and security policies are evaluated (device, location, risk, MFA, etc.).
  1. If allowed, the user gets access to the requested resource without needing to repeatedly reenter credentials (SSO).

Azure AD vs traditional Windows Active Directory

Although the names sound similar, Azure AD and on‑premises Windows Active Directory solve slightly different problems.

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Aspect Windows Active Directory Azure Active Directory (Entra ID)
Deployment model On‑premises directory service running on domain controllers. Cloud-based identity and access service hosted in Azure.
Primary use Managing Windows domain-joined computers and on‑premises resources. Managing access to cloud apps (Microsoft 365, SaaS) and hybrid resources.
Protocols Kerberos, NTLM, LDAP. OAuth 2.0, SAML, OpenID Connect, REST APIs.
Structure Hierarchical: forests, domains, organizational units. Flat structure within a tenant (users, groups, apps).
Device management Group Policy Objects for domain-joined Windows devices. Cloud device management via Intune and related services.
Many organizations run both, synchronizing accounts from on‑prem AD into Azure AD for a hybrid identity setup.

Popular features in real-world use

Modern deployments lean heavily on Azure AD’s security and productivity features.

  • Single sign-on to thousands of SaaS apps and custom apps.
  • Multifactor authentication and passwordless options (e.g., FIDO2 keys, Authenticator app).
  • Conditional Access to adapt requirements based on risk, location, or device state.
  • Self-service password reset and group management to reduce IT helpdesk load.
  • B2B collaboration for partners and vendors, and B2C identity for customer-facing apps.

During and after the 2020 shift to remote work, Azure AD adoption accelerated because it made secure access to Microsoft Teams, Microsoft 365, and other cloud apps much easier for distributed workforces.

Mini example

Imagine a company that:

  • Uses Microsoft 365, Salesforce, and a custom HR portal.
  • Has employees working remotely on various devices.
  • Wants to enforce MFA when staff log in from outside the corporate network.

With Azure AD, they create users and groups, assign app access at group level, enable SSO, and configure Conditional Access policies that ask for MFA when sign-ins look risky.

Employees get a smoother sign-in experience, while IT keeps tighter control and better audit capabilities.

Information gathered from public forums or data available on the internet and portrayed here.