Often, data used in a spatial database is imported from other sources. As such, it may not be in a form that is useful for our current application. In such a case, it may be useful to write functions that will aid in transforming the data into a form that is more useful for our application. This is particularly the case when going from flat file formats, such as shapefiles, to relational databases such as PostgreSQL.
A shapefile is a de facto as well as a format specification for the storage of spatial data, and is probably the most common delivery format for spatial data. A shapefile, in spite of its name, is never just one file, but a collection of files. It consists of at least *.shp (which contains geometry), *.shx ...
