In order to function properly as an Internet address, each domain name must be unique. Domain names as used on the Internet are not only addresses, but also function as a form of expression or communication. Domain names convey ideas and transmit organizational identities. They can be and are put to creative uses. They are often selected to attract attention, and in some cases they form phrases.
Domain names can make reference to people, institutions, and events.
Since the mid-1980s, the communication capabilities of domain names have been restricted by fixed limits on the number of TLD strings. These limits are artifacts of the Internet's historical status as a restricted medium for military and scientific networking. The original designers of the domain name system envisioned a restricted network of a few thousand users equally balanced among educational, corporate, governmental and military organizations. Once the Internet was opened to commercial and private usage, however, users and entrepreneurs quickly discovered and exploited the communication capabilities of domain names. The domain name ceased being a rigid hierarchy analogous to a postal address, and became more analogous to a statement or a brand name.