The use of simple names as a substitute for a numerical address on computer networks precedes the development of the commercial Internet, dating back to the early days of the Advanced Research Projects Agency Network (ARPANET). Today, the primary function of domain names remains to serve as an easily memorized name for an online location, be it a website or a server.
Used in a variety of networking contexts, domain names are most commonly associated with their role in representing an Internet Protocol (IP) resource, like a website, the server hosting that website, or a computer connected to the Internet.
Domain names are divided into levels of the DNS root zone, with the first level being the top-level domain (TLDs), which includes generic top-level domains (gTLD), like .com, .net, .org and .info, and country code top-level domains, or ccTLDs. Lower on the hierarchy are second- and third-level domain names, which are generally available for registration by end-users, businesses and individual website operators. Registration of domain names is typically handled by domain name registrars that offer their inventory for public sale.