File extension BAK is given to files used for backup of another document, often created automatically by various programs or the operating system; for example, Windows may create BAK files for the System.ini and Win.ini files.

TMP files are used to store temporary information. Typically these files are stored only while information in them is needed by an application or operating system and are deleted as soon as this information becomes obsolete.

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

In computing, DLL (an abbreviation of 'Dynamic Linked Library') is a file extension for executable libraries. DLL files are commonly used by software programs to store parts of the executable code.

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.

Files with extension DWG are usually used to store two and thre dimensional data used in engineering. Typical examples of software which use this format is Autocad, IntelliCAD, Caddie and Open Design Alliance applications. DWG is short for drawing. The .bak (drawing backup), .dws (drawing standards), .dwt (drawing template) and .sv$ (temporary automatic save) files are also DWG files.

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.

Microsoft PowerPoint (file extension PPTX) is a presentation program developed by Microsoft. It is part of the Microsoft Office system. Microsoft PowerPoint runs on Microsoft Windows and the Mac OS computer operating systems. It is widely used by business people, educators, students, and trainers and is among the most prevalent forms of persuasion technology. Beginning with Microsoft Office 2003, Microsoft revised branding to emphasize PowerPoint's identity as a component within the office suite. Microsoft began calling it Microsoft Office PowerPoint instead of merely Microsoft PowerPoint. The current version is Microsoft Office PowerPoint 2007. As a part of the Microsoft Office suite, PowerPoint has become the world's most widely used presentation program.

DAT file extension could represent following file types:

- Data file

- A data file extension used to designate an error message in a inbound internet email message (Microsoft Exchange Server v 5.0)

- WordPerfect Merge Data

- Extension used for some MPEG files

- Yahoo Messenger archive file

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.