A ZIP Code is a geographical code used to identify a location or an area. It is used to help identify a specific place by combining a variety of geographic coordinates such as street address, city, county, state, and country in a five-digit code. For example, a ZIP Code of 90210 for the city of Beverly Hills, California, is comprised of the numbers 9, 0, 2, 1, and 0.

ZIP Codes can be used for a variety of GIS uses, including but not limited to:

1. Determining location: By utilizing a layer of ZIP Codes, GIS users can quickly and accurately identify the exact location of an address point.

2. Establishing proximity: By overlaying ZIP Codes onto additional data, GIS can accurately analyze distances from locations to events or points of interest.

3. Spatial analysis: Once spatial data is mapped with ZIP Codes, GIS users can analyze it in order to determine correlations or trends related to demographic information associated with each code.

4. Creating targeted maps: ZIP Codes can be combined with other data to create detailed maps tailored to specific audience groups. For example, they can include data related to areas with high concentrations of certain ages or consumer habits.

One example of the use of ZIP Code in GIS is the creation of a drive-time map. By utilizing a combination of ZIP Codes and road network data, users can identify how much time it takes to drive from one point to another.

In conclusion, ZIP Codes in GIS are an essential reference layer for accurately providing location and analyzing GIS data. They also offer a variety of powerful analytical capabilities, such as proximity and demographic analysis, that are essential for decision making.