PNG files are used to store bitmap images. This format was developed as an alternative to GIF files but without patents burden and with additional features like transparent backgroud. Files with the PNG file extension use indexed colors and lossless compression. PNG files cannot be animated like GIF images.

A PST file is a personal storage directory in which copies of your email messages, calendar events, rules, signatures, and even Microsoft Outlook interface settings are stored. In versions of Outlook 97 through 2002, the storage limit of a PST file for a user is 2 GB. As of Outlook 2003, the limit is 20 GB. It is not recommended, under any circumstances, to try to modify a PST file or move it to another location as errors could occur and it would be necessary to recreate it from Outlook.

A BUP file is a backup file of an IFO file that has been copied from a DVD. It contains a large amount of data related to the content of the DVD and can be accessed if the IFO file cannot be read for whatever reason.

PHP files are used to store code written in Hypertext Language or PHP, a computer language used in web development to create dynamic pages. PHP code allows to create a web page which can display according to several parameters, such as user location, type of client equipment (mobile, PC, etc). Often used to create spaces for members, it is associated with other code systems (CSS, HTML, etc.).

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.

A PKG file, diminutive of "Package", is simply a package of installation files. These files are used by the Mac Operating System and are executed when a user wants to install a program or software on a computer.

Files with CTG extension refer to catalogs used by Canon digital cameras. These CTG files are usually stored in the CANONMSC folder of your Canon digital camera, so when you connect it to your computer through a USB connection, you can access them.

The AAE file extension is associated with the latest format of sidecar XML files, introduced in Apple iOS 8 devices (iPhone 5 and later) and Mac OS Yosemite to support non-destructive image / video editing including effects. The .AAE files are located next to the corresponding image files.

WPS file is similar to the DOC format. WPS files are text documents created with the Microsoft Works Word Processor (MWWP) word processor. Unlike Microsoft Word, this program does not offer advanced formatting options, such as macros. WPS files are efficient for basic text documents, such as notes, spreadsheets, database information and documents whose final product does not need complex effects or formats. Almost all versions of Word can open WPS files, but this format was suspended in 2006, when it was replaced by the DOC extension.

The EPUB (electronic publication) file format is an electronic book format with the extension .EPUB. It is possible to download EPUB files and read them on smartphones, tablets, electronic readers or computers.

File Extension EPUB is used to store electronic books files. EPUB is an electronic book format defined by the International Digital Publishing Forum.

Today, any operating system, whether PC, mobile or even embedded, has the software pre-installed natively to, at least, open JPG file. Windows, Mac OS, iOS, Android are all capable to open JPG files without additional installed software.