DWG refers to both a technology environment and .dwg files, the native file format for Autodesk's AutoCAD® software.
AutoCAD .dwg file format
Autodesk created .dwg in 1982 with the very first launch of AutoCAD software. DWG files contain all the information that a user enters in a CAD drawing. This data can include:
Maps and photos
The .dwg file format is one of the most commonly used design data formats, found in nearly every design environment.
DWG technology environment
The DWG technology environment contains the ability to mould, render, draw, annotate and measure. While commonly associated with AutoCAD, DWG technology is an integral part of many of our CAD products (AU site).