A domain in networking refers to a logical grouping of computers, devices, users, and resources that are organized and managed under a single administrative framework. This structure allows centralized management of network policies, security, authentication, and resource access.
A server (or servers) called a domain controller manages the domain. It authenticates users, enforces policies, and manages directory information such as user accounts and security groups. Users log in using domain credentials, which allows them to access authorized resources from any device within the domain, not just their personal workstation. Large organizations may use multiple domains connected by trust relationships, enabling secure resource sharing across different parts of the organization.