Closed TLDs exist because they are intended for limited use or needed for testing or documentation purposes. The Internet Engineering Task Force (IETF) reserved the DNS labels .invalid, .example, .localhost and .test to allow for easy testing on websites without confusion. Restricted TLDs were created with a very specific purpose. American users are familiar with .gov and .mil, two rTLDs (restricted Top Level Domains) that are to be used exclusively for government and military purposes. Similarly, .edu extension is also restricted and only accredited institutes or US-based post-secondary institutions can use it. Find out more about how TLDs work.