A ZIP Code is a five-digit numeric code that identifies a collection of mailing addresses within the USA, to simplify the distribution of mail by the USPS. In general, a ZIP Code is a delivery sort sequence and the USPS does not associate an area with each ZIP Code.

The 5-digit ZIP number is a structured code in which the first digit identifies one of ten large areas of the Nation. Groups of states (or equivalent areas) number from 0 in the Northeast to 9 in the West.

The second digit of a 5-digit ZIP Code indicates a State, a geographic portion of a heavily populated State, or two or more less populated States.

3-digit ZIP Codes are a collection of 5-digit ZIP Codes with the same first three digits. For example, the "165" 3-digit ZIP Code comprises all 5-digit ZIP Codes that begin with "165." They identify a major area within a State, which may be a large city post office or a major mail concentration point (Sectional Center) in a less populated area.

Some 3-digit ZIP Codes, and their associated 5-digit ZIP Codes, do not form contiguous areas. For example, 683 and 684 when merged together form a contiguous area. 683 contains all the 5-digit ZIP Codes whose "name" (often the associated town or neighborhood name) begins with the letter A-L, while 684 contains all the 5-digit ZIP Codes whose "name" begins with the letter M-Z. They are the ZIP Codes that surround Lincoln, Nebraska ZIP 685.

Many 5-digit ZIP Codes can be shown as areas. For example, those ZIP Codes that encompass multiple addresses, and ZIP Codes for buildings or campuses that have defined borders. The boundaries of the ZIP Code areas are created by, for example, grouping small areas (defined by the Census Bureau) based on the dominant ZIP Code of the addresses in each small area. Some can even be a single block, such as 16544.

Five-digit ZIP Code Tabulation Areas (ZCTAs) are based on Census blocks and are distinct from USPS-based postal areas. Maptitude 5-digit ZIP Code area layers are much more accurate than ZCTAs because they are based on Census areas that are smaller than a block. This greater detail allows Maptitude ZIP Code areas to better follow actual deliverable addresses. In addition, the Maptitude ZIP Code area layers extend into undeliverable areas to encompass the entire USA and are updated annually to account for USPS changes to ZIP Codes.

Every ZIP Code can be shown as a point. The point is at the Post Office for the ZIP Code, if there is one, or at a central location inside the ZIP Code area where the ZIP Code can be shown as an area. ZIP Codes are also shown as points when they can't be shown as an area such as 5-digit ZIP Codes for a single business, building, or PO Box. For example, ZIP Codes 16522, 16530, 16534, 16538 and 16553.

A ZIP+4 code is an extension to the standard 5-digit ZIP code used by the USPS to further specify a location for mail delivery. It consists of the original 5-digit ZIP code followed by a hyphen and four additional digits. The additional digits help to identify a more specific geographic area, such as a specific house, block or group of addresses within the 5-digit ZIP code area. The ZIP+4 code is used to improve the accuracy and efficiency of mail sorting and delivery.

The USPS divides each ZIP Code into carrier routes. A USPS carrier route is a grouping of addresses that are near each other. Each carrier route is identified by a unique code that consists of the original 5-digit ZIP code followed by a letter and 3 numbers. The letters are H for Contract, R for Rural, and C for City. Each carrier route includes a list of addresses that the carrier is responsible for delivering mail to. This allows for more efficient and organized mail delivery within a given area. As for 5-digit ZIP Codes, they are not defined as areas by the USPS, but a central point for each such list of addresses can be displayed on a map.

A USPS Post Office (PO) Box is a secure and convenient way to receive mail when a physical address is not available or preferred. These are mapped as 5-digit ZIP Code points and are often located with many other such points at a specific Post Office location.