answer:A top-level domain (TLD), sometimes referred to as a top-level domain name (TLDN), is the last part of an Internet domain name; that is, the letters which follow the final dot of any domain name. For example, in the domain name
http://www.example.com, the top-level domain is com (or COM, as domain names are not case-sensitive). Management of most top-level domains is delegated to responsible parties or organizations by the Internet Corporation for Assigned Names and Numbers (ICANN), which operates the Internet Assigned Numbers Authority (IANA) and is in charge of maintaining the DNS root zone. — In addition to the Internet’s main DNS root (currently consisting of 13 nominal root nameservers working in agreement with ICANN), several organizations operate alternative DNS roots (often referred to as alt roots). Each alternative root has its own set of root nameservers and its own set of top-level domains (TLDs). The Internet Architecture Board has spoken out strongly against alternate roots in RFC 2826, “IAB Technical Comment on the Unique DNS Root”.