Design Web Format (DWF) represents 2D/3D drawing in compressed format for viewing, reviewing, or printing design files. It contains graphics and text as part of design data and reduces the size of the file due to its compressed format. The reduced file size makes the distribution and communication of rich design data efficient. DWF doesn't require the recipient to know about the usage of CAD software that created the original drawing.
PNG, Portable Network Graphics, refers to a type of raster image file format that use loseless compression. This file format was created as a replacement of Graphics Interchange Format (GIF) and has no copyright limitations. However, PNG file format does not support animations. PNG file format supports loseless image compression that makes it popular among its users. With the passage of time, PNG has evolved as one of the mostly used image file format.
You can also convert DWF into many other file formats. Please see the complete list below.