A postal or postcode is a numerical code post authorities assign to a specific region or area within a country. These codes consist of digits, though alphanumeric combinations may appear in specific situations. The length and structure of postal codes vary depending on the country and postal system. Articles What Are Postal Codes? Postal codes are strings of numbers (and sometimes letters) that help postal services determine where a piece of mail is being sent to. They help simplify the task of bringing post to its destination. Postal codes are a set of numbers, a particular set of numbers (although it sometimes includes letters too) that helps postal services determine the destination of a mail. The postal code allows mail to reach its destination, and full ZIP+4 ensures it reaches the destination ASAP. .