File with DOWNLOAD file extension usually contains an incomplete download started by Apple Safari web browser. Apple Safari adds .DOWNLOAD file extension to a file name when it starts downloading. When downloading process is done .DOWNLOAD file extension removed from the file name.

Office Open XML (also referred to as OOXML or Open XML) is an ISO/IEC standardized ZIP-compatible file format originally developed by Microsoft for representing spreadsheets, charts, presentations and word processing documents. Starting with Microsoft Office 2007, the Office Open XML file formats (ECMA-376) have become the default file format of Microsoft Office.

Office Open XML (also referred to as OOXML or Open XML) is an ISO/IEC standardized ZIP-compatible file format originally developed by Microsoft for representing spreadsheets, charts, presentations and word processing documents. Starting with Microsoft Office 2007, the Office Open XML file formats (ECMA-376) have become the default file format of Microsoft Office.

MKV file extension is used for files in Matroska multimedia container format. Matroska file format was created in 2002 based on the Multimedia Container Format. Matroska format and MKV file is widely popular storage format for multimedia files on the internet.

SWF file extension is used to store Adobe Flash multimedia file format. SWF (pronounced “swiff”, short for “Shockwave Flash”) file format was developed by FutureWave Software Inc in 1995 and released as a storage format for FutureSplash Animator software on Windows and Mac OS.

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.

ICS file extension is used by iCalendar internet standard to store events, to-dos, free/busy information and journal entries. The ICS file format is defined in RFC-5545 specification.

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.

JavaScript Object Notation (JSON) is a format used to store structured data in JavaScript derived data format. JSON was designed by Douglas Crockford while his work in State Software. JSON at that time was designed to exchange application state information between web application and back-end server.

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.