A telephone number is a unique series of digits assigned to a telephone line, allowing individuals to make and receive calls. Typically, a telephone number consists of an area code, followed by a local number. The area code identifies a specific geographic region, while the local number connects to a particular phone within that area. Telephone numbers can vary in format depending on the country. For example, in the United States, a standard number is formatted as NXX-NXX-XXXX, where "N" represents a digit from 2 to 9, and "X" represents any digit from 0 to 9. This system helps organize and route calls efficiently.