A file with .igs (Initial Graphics Exchange) extension is a 2D-3D design exchange file format that is independent of source or destination file format specifications used by CAD applications. It is used to exchange design information about circuit diagrams, wireframes, the freeform surfaces between two independent systems. IGS files can be opened by applications such as Autodesk, FreeCAD, CADEX CAD Exchanger, and other similar applications.
Files with POTM extension are Microsoft PowerPoint template files with support for Macros. POTM files are created with PowerPoint 2007 or above and contains default settings that can be used to create further presentation files. These settings can include styles, backgrounds, colour palette, fonts and defaults along with macros that consist of custom functions for doing particular task. They may also be opened by a previous version of PowerPoint with Open XML document support installed. POTM files can be opened in Microsoft PowerPoint for editing like any other PowerPoint file.
You can also convert IGS into many other file formats. Please see the complete list below.