A domain, often referred to as a realm, is a specific area of knowledge, activity, or influence. In the context of the internet, a domain is a unique address that identifies a website, such as example.com. It helps users easily navigate to different online locations and is essential for organizing the vast amount of information available on the web. In computer science, a domain can also refer to a collection of resources, such as computers and users, that are managed under a common administration. This is often seen in Active Directory, where a domain allows for centralized management of user accounts and security policies within a network.