Geographic area codes are numerical prefixes used in telephone numbers to designate specific regions or locations within a country. In the United States, for example, area codes are typically three digits long and help route calls to the correct geographic area. Each area code corresponds to a particular region, allowing for efficient communication across vast distances. These codes are part of the North American Numbering Plan (NANP), which includes countries like Canada and Mexico. Area codes can also indicate population density; more populous areas often have multiple area codes to accommodate the high volume of phone numbers needed.