This document provides an overview of Microsoft Azure Active Directory (Azure AD). Azure AD is a cloud-based identity and access management service that allows users to be authenticated and granted access to resources. It can be extended with Azure AD Domain Services to manage Azure virtual machines like a traditional on-premises Active Directory. There are different pricing tiers for Azure AD including a free tier. Setting up Azure AD Domain Services involves enabling the feature and configuring DNS. Administrators can then join Azure VMs and manage policies from Azure AD.