A Shape file is a GIS file which is for use with ArcView software and other GIS packages.  Although commony termed a shape file, it actually consists of three different files: the shape file (.shp extension), the shx file (.shx extension), and the dbase file (.dbf extension).  These three files together are recognized by ArcView as a GIS data set and may be used directly by ArcView or imported into other GIS software packages for use.