gSpatial Toolbar is aimed at users who have a requirement for integrating third party GIS data and possibly their own data with Google Earth. Google Earth has become an industry standard in terms of representing geographical or mapping data, but the free version of Google Earth does not provide you with the ability to use GIS exchange formats like shapefiles directly. The gSpatial toolbar addresses this gap.

gSpatial Toolbar is a software program that allows you to use ESRI shapefiles along with Google Earth. An ESRI shapefile is a very common, binary map or GIS exchange format file, which is often used to exchange data between differing Geographical Information Systems (GIS) software packages such as ESRI's ArcInfo or MapInfo. You can also purchase or download ESRI shapefiles from commercial or public data vendors, such as the US Census Bureau. The problem with shapefiles is that, although the binary format is published and well-known, it is pretty difficult for non-programmers to convert shapefiles to another format such as Google Earth's without doing some programming themselves.

Google Earth uses a variant of XML called KML to do its data exchange, for example to import external geographical features. You can read about KML here. The gSpatial Toolbar is a way of automatically using shapefiles with Google Earth. It does so by converting the binary data in shapefiles to KML and then opening the KML in Google Earth.

In addition to simply loading the geographical features (or geometries) that live in shapefiles, gSpatial Toolbar also allows you to preview the data in its own viewer (separate from Google Earth) and to perform queries on your data. An example of a query is to shade countries with different colors, according to their population densities.

gSpatial is supplied in two variants: a freeware version, the one you've downloaded, and a Professional Version that offers enhanced functionality, such as the ability to perform customized exports based on geographical or attribute based selections.