AD DS is the main service in AD, which is a crucial identity and access management (IAM) solution within the Windows Server operating system (OS) environment. AD DS stores and manages information about users, services, and devices connected to the network into a tiered structure. AD DS allows IT teams to streamline IAM services by serving as a centralized point of administration for all the activities on the network. The servers that host AD DS are domain controllers (DCs). An organization can have multiple DCs, with each one storing a copy of the AD DS for the entire domain. Most organizations use AD DS to manage on-prem IAM in Windows environments. However, you can also replicate it in Azure if you’re hosting your applications partly on-prem and partly in Azure.