A domain is a unique address used to identify a website on the internet. It typically consists of a name (such as "example") and a domain extension (like ".com" or ".org"), forming a complete web address (e.g., example.com). Domains make it easy for users to access websites without needing to remember complex numerical IP addresses. They are registered through accredited registrars and play a crucial role in branding, online presence, and digital communication.