A domain is a unique name that identifies a website or online service on the internet, such as example.com. Domains make it easy for users to access websites without needing to remember complex numerical IP addresses. They are managed through the Domain Name System (DNS), which translates domain names into IP addresses that computers use to locate each other online. Domains are essential for branding, credibility, and accessibility on the web, and are typically registered through accredited domain registrars.