A GIS file format is a standard of encoding geographical information into a file. They are created mainly by government mapping agencies (such as the USGS) or by GIS software developers.
Metadata often includes:
Elevation data, either in raster or vector form (e.g., contours)
Shape layers, usually expressed as line drawings, for streets, postal zone boundaries, etc.
Coordinate system descriptions.
One or more datums describing the precise shape of the Earth assumed by the coordinates.