A DWG file is a database of 2D or 3D drawings created with AutoCAD. It contains vector image data and metadata describing the contents of the file. DWG files are related to .DXF files, which are ASCII versions of DWG files.
PLY is a computer file format known as the Polygon File Format or the Stanford Triangle Format. It was designed to store three-dimensional data from 3D scanners. The data storage format supports a relatively simple description of a single object as a list of nominally flat polygons.