In the context of networking and the Internet, a domain refers to a sphere of knowledge identified by a name. Specifically, in terms of domain names, it’s part of a network address that identifies it as belonging to a particular domain. This is used to control internet addresses under the DNS (Domain Name System), which translates domain names to IP addresses. Domains also refer to specific areas of control or influence, such as a security domain in information security or a collision domain in networking.