TLD = Top Level Domain (name) is the final and most significant part of a domain name only. A dot com (".com") or dot co dot UK (".co.uk") are examples of top level domains. Further, "http://www.google.com" is a TLD but "http://images.google.com" (a subdomain) and "http://www.google.com/webmasters/page.html" (a page on a 2nd level directory) are both addresses that are not top level domains.