STL is a file format native to the Stereolithography CAD software created by 3D Systems. This file format is supported by many other software packages; it is widely used for rapid prototyping and computer-aided manufacturing. STL files describe only the surface geometry of a three dimensional object without any representation of color, texture or other common CAD model attributes. Many Computer-aided design systems are able to output the STL file format among their other formats because it's quick and easy to implement.
STL file output is almost always available from a CAD system; it's often used as a quick method for importing the necessary geometry into the CAM system. Many integrated CAD and CAM systems transfer their geometric data using this file format, because it's impossible to go wrong.

DWF (Design Web Format) is an open, secure file format developed by AutoDesk for the efficient distribution and communication of design data to anyone who needs to view, review, or print design files. Because DWF files are highly compressed, they are smaller and faster to transmit than design files, without the overhead associated with complex CAD drawings.

DWF files are not a replacement for native CAD formats such as AutoCAD drawings (DWG). The sole purpose of DWF is to allow designers, you, engineers, and project managers, to communicate design information and design content.AutoDesk Design Review is a free viewing application that enables all members of the project team to easily view, measure, markup and print designs shared electronically. Built around the DWF file format, Design Review enables users to view and print complex 2D and 3D drawings, maps, and models published from AutoDesk design applications or from the DWF Writer.