PDF is short for "Portable Document Format" which was created by Adobe Systems in 1993 to facilitate document exchange. After creation of the internet this format experienced significant growth and became de-facto standard for document exchange on the internet.

MUI, or multilingual user interface files are language resource files used by Windows operating systems as of version 2000 and above, and allow the interface to display different languages. While files with the MUI extension are usually associated with the Windows interface, they can also be created by Open GL tools.

The ZI extension represents the popular ZIP file, with a different name, to avoid mail and messaging server filters. Within the archive, there is at least one single file of any type.

GPX is the standard file extension for the exchange and storage of map and route data on GPS devices, smartphones and computers.

A file with DXF extension (acronym for Drawing Exchange Format) is a file format for CAD design drawings that belongs to the AutoCAD program group, and is used to save the drawings created by those programs. This type of files allows interoperability between the DWG files, proprietary file format of the AutoCAD program, and the rest of the programs on the market, proprietary or license free.

A STEP file is used to store 3D models formatted in an ISO 10303-21 standard for the purpose of the exchange of 3D product data. It contains three-dimensional data in a format that can be recognized by various programs.

A file with an STP extension contains the 3D object project that meets the standards of the STEP format (Standard for exchanging product data). STP files are similar to STEP files in terms of structure and format, STEP is just less used.

Most frequent use of RAR extension is to store compressed information archived using RAR format. It is a proprietary compression format developed by Eugene Roshal. Compressing files is very useful when you want to transfer them over the internet since compression reduces amount of information to transfer. Also you may fit much more information on your PC hard drive if you compress information that you don't use.

ZIP file extension is used for archive files compressed with DEFLATE algorithm of lossless compression.

You can open XLSX file using Microsoft Excel application. Microsoft Excel is similar to other spread sheet applications that can store information that can be edited and viewed on several platforms. You can run Microsoft Excel and open XLSX files on Mac and Windows through installed Microsoft Office applications.