tld means top-level domain. It is the extension letter immediately after the final dot in url address. Generally we call it as dot com (.com) while referring to any website.
A TLD identifies website with its purpose, such as organization or geography. There are many tlds – .com, .in, .info. org etc. Each tld has a separate registry handled by a designated agency under the direction of ICANN – Internet Corporation for Assigned Names and Numbers
A full qualified domain name called as FQDN in short, constitutes https://99mag.com in our url.
If we break down the following url http://academy.99mag.com – then
com is the top level domain
99mag is second level domain
academy is sub-domain and
the addition of HTTP:// makes an FQDN a complete URL.
As told previously – All together, forms fully-qualified domain name