The full form of FQDN is Fully Qualified Domain Name. It’s used on Computing ,Internet in Worldwide

Fully Qualified Domain Name (FQDN), also referred to as an absolute domain name, is a domain name that specifies its exact location in the tree hierarchy of the Domain Name System (DNS). Usually an FQDN consists of a host and domain name, and a Top-Level Domain (TLD). FQDN provides enough information so that it can be converted into a physical IP address. FQDNs are used to specify the exact location of a webpage or webserver to a client.

A FQDN is mostly consist of three levels:

1) The appendage of the domain is the Top Level Domain (TLD). Example: com, net or org

2) The domain name will be inserted in front of the TLD. Example: companyname or websitename

3) At the very first stands the hostname. For webpages mostly: www

For example, www.fullforms.com is a fully qualified domain name, where www is the host, fullforms is the second-level domain (domain name), and .com is the Top Level Domain (TLD).