AWS Directory Service is a managed service provided by Amazon Web Services (AWS) that enables organizations to connect and integrate their AWS resources with existing on-premises or cloud-based Microsoft Active Directory (AD) environments. It simplifies the management of user directories, user authentication, and authorization processes.

AWS Directory Service offers the following directory options:

1. AWS Managed Microsoft AD: This option provides a fully managed Active Directory service hosted by AWS. It is compatible with Microsoft AD, allowing you to seamlessly extend your on-premises AD infrastructure to the AWS cloud. With this service, you can join EC2 instances to the domain, manage users and groups, and run Active Directory-dependent applications.

2. Simple AD: This option is a cost-effective alternative to AWS Managed Microsoft AD. It is a standalone directory based on Samba 4, which is compatible with applications that use Microsoft AD for authentication. Simple AD allows you to manage users, groups, and domain-joined EC2 instances within the AWS environment.

3. AD Connector: AD Connector acts as a proxy between AWS applications and your existing on-premises Microsoft AD infrastructure. It allows you to use your existing AD credentials to authenticate and authorize access to AWS resources. With AD Connector, you don’t need to synchronize user accounts or passwords to the cloud, as authentication is performed against your on-premises AD.

4. Amazon Cloud Directory: Amazon Cloud Directory is a fully managed directory service that enables you to build flexible and scalable directories for organizing hierarchies of data. It is designed to store and retrieve large amounts of hierarchical data, such as organization charts, course catalogs, and device registries.

By utilizing AWS Directory Service, organizations can centralize user management, simplify authentication and authorization processes, and enable secure access to AWS resources. It streamlines the integration between on-premises and cloud environments, making it easier to manage hybrid infrastructure and support various applications that rely on Active Directory.