Azure Active Directory (Azure AD) is Microsoft’s multi-tenant, cloud-based directory, and identity management service that combines core directory services, application access management, and identity protection into a single solution. Azure AD also offers a rich, standards-based platform that enables developers to deliver access control to their applications, based on centralized policy and rules.
Azure Active Directory comes in four editions—Free, Basic, Premium P1, and Premium P2.
All Microsoft Online business services rely on Azure Active Directory (Azure AD) for sign-in and other identity needs. If you subscribe to any of Microsoft Online business services (for example, Office 365 or Microsoft Azure), you get Azure AD with access to all of the Free features. With the Azure Active Directory Free edition, you can manage users and groups, synchronize with on-premises directories, get single sign-on across Azure, Office 365, and thousands of popular SaaS applications like Salesforce, Workday, Concur, DocuSign, Google Apps, Box, ServiceNow, Dropbox, and more.
To enhance your Azure Active Directory, you can add paid capabilities using the Azure Active Directory Basic, Premium P1, and Premium P2 editions. Azure Active Directory paid editions are built on top of your existing free directory, providing enterprise class capabilities spanning self-service, enhanced monitoring, security reporting, Multi-Factor Authentication (MFA), and secure access for your mobile workforce.
Check the full Editions details here