The term "NPA-NXX" refers to a specific format used in telephone numbering in North America. "NPA" stands for "Numbering Plan Area," which is commonly known as the area code. The "NXX" represents the next three digits of a seven-digit phone number, indicating a specific exchange within that area code. Together, they help route calls to the correct geographic location. For example, in the phone number 555-1234, "555" is the NPA, while "1234" is the last four digits of the number. This system is essential for organizing and managing telephone services across various regions, ensuring efficient communication.