A directory service is a database that stores information about users and resources on a network, allowing companies to manage access, authentication, and authorization. Common providers include Active Directory, Google Workspace Directory, Apache Directory Server, Red Hat Directory Server, Apple Open Directory, and Okta universal directory. Companies use directory services for increased security, simplified account management, improved compliance posture, and better user experience. They work through a client-server model with a centralized database that stores information about network resources such as users, groups, devices, and services.