Active Directory is a directory service developed by Microsoft for managing computers and other devices on a network. It helps organizations store information about members of the domain, including users, groups, and devices, and provides a way to manage permissions and access to resources. With Active Directory, administrators can create and manage user accounts, enforce security policies, and organize resources in a hierarchical structure. This makes it easier to control who can access what within an organization, ensuring that sensitive information is protected while allowing users to collaborate effectively.