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.

EPS file extension is used to store information in Encapsulated Postscript format. Encapsulated Postscript is a subset of Postscript language which is used to deliver commands and information to the printer. EPS files are used to store and exchange graphic content.

CSV file extension is used by files in comma separated values format. CSV files typically contain table information. First line of CSV file usually contains a table header and other lines contain table rows with data. Each line in CSV file consists of text strings delimited by commas. Each text string can contain any symbols except of the comma. If comma needs to be used inside the string, then string should be enclosed in quotes.

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.

NUMBERS file extension is used to store files in Apple Numbers office application file format. Apple Numbers is a free application from Apple used to create and edit spreadsheets.

PAGES if a file extension used by Apple Pages word processing software. Apple Pages was initially released for Mac OS in 2005. It is distributed as part of iWork Suite and also as an individual application. Apple Pages is integrated with iCloud service and allows editing documents on any device using web browser.

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.

KEY file extension is used to store files in Apple Numbers office application file format. Apple Numbers is a free application from Apple used to create and edit spreadsheets.

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.