A telephone number is a unique series of digits assigned to a telephone line, allowing individuals to make and receive calls. It typically consists of an area code, which identifies a specific geographic region, followed by a local number that connects to a particular phone. Telephone numbers can vary in length depending on the country, but they usually range from 7 to 15 digits. They are essential for communication and are often used in various services, such as emergency services, business contacts, and personal communication.