What is a phone number?
A telephone number is essentially your address within the telephone system. As with a postal address, it contains several layers of information. Your telephone number consists of a telephone country code, a city code or area code (in most, but not all, countries), and a subscriber number. You must dial the entire number, beginning with the country code, when calling from outside your own country, but you can usually dial only part of the number when calling locally or within your own country.