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.
Designed to empower organizations with more demanding identity and access management needs, Azure Active Directory Premium edition adds feature-rich enterprise-level identity management capabilities and enables hybrid users to seamlessly access on-premises and cloud capabilities. This edition includes everything you need for information worker and identity administrators in hybrid environments across application access, self-service identity and access management (IAM), identity protection and security in the cloud. It supports advanced administration and delegation resources like dynamic groups and self-service group management. It includes Microsoft Identity Manager (an on-premises identity and access management suite) and provides cloud write-back capabilities enabling solutions like self-service password reset for your on-premises users.