ESRI shapefiles are a very common type of mapping or Geographical Information System (GIS) binary exchange file format, used to share data between different GIS applications. Many commercial vendors or government departments supply electronic mapping data in a shapefile format. Sample shapefiles for the United States are installed to your hard disk during the installation.

Each shapefile dataset will consist of 3 or more individual files. (In the rest of this help documentation, the collective name "layer" will be used for the combination of these 3 files) These files have the same name but different extensions. These are .shp, .shx and .dbf. A typical shapefile containing countries could have 3 files called country.shp, country.shx and country.dbf. Collectively, these are known as a layer or just a shapefile. A layer can be thought of as a transparency that can be overlaid on top of other layers. One layer could for example contain countries, the other roads, and yet another capital cities.

A shapefile dataset has a geometry file (the .shp file), which contains feature coordinates in a binary format. A feature is one entity on a map, for example a country or a road. A shapefile dataset may contain only one type of feature. For example, it can only contain polygons, lines or points, but not mixtures of the above. Each feature can have multiple parts - for example, the island chain of Hawaii has multiple islands but it is only one state of the United States. Each part, in turn, can have multiple coordinate pairs. A coordinate is a latitude / longitude or X-Y value.

Please take very careful note of the following: Google Earth wants to work with Latitude/Longitude coordinates expressed in decimal degrees. Shapefiles can, however, contain any type of coordinate, such as x-y coordinates in meters. If your shapefile does not contain coordinates expressed in decimal degrees, Google Earth will not be able to display it, and the gSpatial Toolbar will warn you if it considers the coordinates to be of a different type. Unfortunately there is no way to tell what the coordinate type and projection is if you're not sure about the source. Please contact the supplier or person from whom you obtain your shapefiles. A GIS professional should be able to convert your shapefile's coordinates from other formats to decimal degrees relatively easily and give you a shapefile that does contain decimal degrees.

Another file in a shapefile dataset, is a spatial index file, with a .shp extension. This is used to speed up feature retrieval.

The third component of a shapefile dataset is the attribute table, with a .DBF extension. As you may gather from the name, a DBF file is a DBase III format database table. The attribute data is non-geometrical, text data that refers to features. For example, if your shapefile contains the geometries of the countries of the world, the attribute table could for example contain the name, population and capital city names of the countries. The order of records in the attribute table is important. Each row or record in the attribute table corresponds exactly to one geographical feature.