Here are a few terms that are often used when referring to FGDL information.

Projection The geographic coordinate system of the data (the positions, often measured in degrees of latitude and longitude, of objects on the earth's spherical surface).

Shapefiles This is the native format of spatial data (themes) used by ArcView. When you create new spatial data in ArcView it is saved in this format. ESRI's white paper (.pdf) on shapefiles explains in great detail the shapefile file format.

Metadata In the simplest terms, metadata is data about data. The metadata is important because it describes what a dataset is as well as describing the background information about a dataset.

Raster A cellular data structure composed of rows and columns for storing images. Groups of cells with the same value represent features.

Vector Coordinate-based data structure commonly used to represent linear geographic features. Each linear feature is represented as an ordered list of points. Traditional vector data structures include double-digitized polygons and arc-node models.

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