A domain is the unique address that identifies a website on the internet. It consists of a domain name and a domain extension (e.g., .de, .com, .org). The domain name serves as a user-friendly version of the IP address, which describes the actual location of a web server hosting the website. Domains play a crucial role in internet navigation by allowing users to access websites via names like "example.com" rather than remembering numerical IP addresses. Domains can be registered by individuals or businesses to establish their presence on the internet. The management of domains is handled by registrars, who oversee the availability and registration of domain names.