A top-level domain (TLD) is the part of the domain name located to the right of the dot (" . "). The most common top-level domains are .com, .net, and .org. Some other popular top-level domains are .biz, .info, .name, and .ws. These common top-level domains have certain guidelines attached, but are for the most part available to any registrant, anywhere in the world.

There are also restricted top-level domains (rTLDs), like .aero, .biz, .edu, .mil, .museum, .name, and .pro, that require the registrant to represent a certain type of entity, or to belong to a certain community. For example, the .name TLD is reserved for individuals and .edu is reserved for educational entities.

Country-code TLDs (ccTLDs) are for Web sites and registrants of a particular geographic location. For example: bz (Belize), .ca (Canada), .dk (Denmark), .ec (Ecuador), ie (Republic of Ireland), .uk (United Kingdom), .us (United States), and .zw (Zimbabwe).