ICANN (Internet Corporation for Assigned Names and Numbers) designates organizations to manage each TLD. Depending on how strict an administrating organization might be, TLD often serves as a clue to the purpose, ownership, or nationality of a website.
Consider an example Internet address:
Here org is the TLD; mozilla.org is the second-level domain name; and developer is a subdomain name. All together, these constitute a fully-qualified domain name; the addition of https:// makes this a complete URL.
IANA today distinguishes the following groups of top-level domains:
- country-code top-level domains (ccTLD)
- Two-character domains established for countries or territories. Example: .us for United States.
- internationalized country code top-level domains (IDN ccTLD)
- ccTLDs in non-Latin character sets (e.g., Arabic or Chinese).
- generic top-level domains (gTLD)
- Top-level domains with three or more characters.
- unsponsored top-level domains
- Domains that operate directly under policies established by ICANN processes for the global Internet community, for example "com" and "edu".
- sponsored top-level domains (sTLD)
- These domains are proposed and sponsored by private organizations that decide whether an applicant is eligible to use the TLD, based on community theme concepts.
- infrastructure top-level domain
- This group consists of one domain, the Address and Routing Parameter Area (ARPA).