A top-level domain (TLD), sometimes mistakenly referred as an Internet extension, is one of the domains at the highest level in the hierarchical Domain Name System of the Internet. The top-level domain names are installed in the root zone of the name space. For all domains in lower levels, it is the last part of the domain name, that is, the last label of a fully qualified domain name. For example, in the domain name www. example. com, the top-level domain is . com (or .