For more, see Layers, Data Management
A layer in GeoSync that contains either point, line, or polygon features corresponds to a shapefile. A Shapefile is actually comprised of 5 separate files, of which the .shp, .dbf, and .shx are required while the .sbn and .sbx are automatically regenerated by GeoSync. Therefore, every Shapefile layer in GeoSync has a set of either three or five corresponding files. The .shp portion of a shape file contains the coordinate information for the map features while the .dbf portion stores the feature attribute data. The .shx is acts as a link between the .shp and .dbf.
Following is a list of the files:
.shp - Feature geometry. Required.
.shx - Index of the feature geometry. Required.
.dbf - Feature Attribute Data of features. Required.
.sbn and .sbx - the files that store the spatial index of the features. Not Required.
Remember: A Shapefile is necessarily a layer in GeoSync but a layer does not have to be a Shapefile! (see Layers)