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.

MPEG-4 Part 14, formally ISO/IEC 14496-14:2003, is a multimedia container format standard specified as a part of MPEG-4. It is most commonly used to store digital audio and digital video streams, especially those defined by MPEG, but can also be used to store other data such as subtitles and still images. Like most modern container formats, MPEG-4 Part 14 allows streaming over the Internet. The official filename extension for MPEG-4 Part 14 files is .mp4, thus the container format is often referred to simply as MP4.

APK file extension is short for Androi Package. It is used to store information about Android deployment packages. APK files are usually used by Android and Google Play to deliver applications to Android devices.

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.

LNK files are commonly known as Windows shortcuts. They are used to refer to local files or remote urls. To view information in LNK file in Windows you can press right mouse button on a LNK file and select Properties from popup menu.

JNLP is short for Java Network Launching Protocol. This format is used by Java to download and launch applications over the network. JNLP applications typically don't run from user internet browser.

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.

CRDOWNLOAD is chrome partially downloaded file. Usually such file cannot be recovered since only part of it was downloaded. You need to visit website with download again and re-download it.

QFX file extension is a open financial exchange file generated by Quicken. It is used to store financial information. QFX files are based on XML format and usually contain financial transactions for certain accounts.