Azure Active Directory is a Microsoft cloud-based identity and access management service. Azure AD helps employees of an organization sign in and access resources.
External resources might include Microsoft Office 365, the Azure portal, and thousands of other software as a service (SaaS) applications.
Internal resources might include apps on your corporate network and intranet, along with any cloud apps developed by your own organization.
Azure AD (Azure Active Directory) provides services such as:
Authentication - This includes verifying identity to access applications and resources, and providing functionality such as self-service password reset, multi-factor authentication (MFA), a custom banned password list, and smart lockout services.
Single-Sign-On (SSO) - SSO enables users to remember only one ID and one password to access multiple applications. A single identity is tied to a user, simplifying the security model. As users change roles or leave an organization, access modifications are tied to that identity, greatly reducing the effort needed to change or disable accounts.
Application Management - You can manage your cloud and on-premises apps using Azure AD Application Proxy, SSO, the My apps portal (also referred to as Access panel), and SaaS apps.
Business to business (B2B) identity services - Manage your guest users and external partners while maintaining control over your own corporate data
Business-to-Customer (B2C) identity services - Customize and control how users sign up, sign in, and manage their profiles when using your apps with services.
Device Management - Manage how your cloud or on-premises devices access your corporate data.