File Extension Cheat Sheet

BASIC EXTENSIONS
exe: Executable, what you actually run. This is a windows program of any sort. normally need a program called OllyDBG or IDA Debugger to modify.
dll: Dynamic Library, houses data for exe's to actually read from. Like a library of data for a program itself. Same tools as above.
txt: Text file, just a basic text file that holds words or info in plain readable and modifiable text. use Notepad or Notepad++ to modify.
ini: Impact Nominal Index, much like a text file, can house code for a exe to execute. Modify with Notepad or Notepad++
dat: Data File. These can vary to being a basic text file, to advanced encrypted unmodifiable files. Range of programs for modifying varies.
cfg: basic config file. Normally these files are encrypted in some way, but this file usually houses game/app settings like Screen Resolution, Pixel depth, Depth Of Field Distance, and much more.
bat: Batch File, the most basic of basic programming that still exists today. More widely used in basic command line situations.

WEB BASED Formats
HTML: HyperText Markup Language, basic webpage files are generally coded in HTML. use Notepad, Notepad++ or Dreamweaver (in advanced situations) to modify permanately. Use Chrome Inspector to do live edits.
php: Personal Hypertext Preprocessor, more advanced web files. Cannot generally see this code on a web server.
css: Cascading Style Sheets, house styling information like text color, background color, image height/width, etc. for a web page to load.
XML: A markup language that houses data for applications. Used widely in old school game save files, settings files, and web design elements for lists of items or objects.
SWF: Adobe Flash file specifically. Many of the in-browser games you play or advertisements you see will be adobe flash swf files. These can be modified with tools like JPEXS Decompiler or SoThink SWF Decompiler. Decompiled files will be in Adobe FLA format

Video Formats
avi: Audio Video Interleaved. Primarily used by Microsoft with Windows Media Player as it's main video format.
MP4: MPEG-4, special high compression format for movies widely used on most platforms. Can have amazing video quality if compressed right.
MKV: BluRay rip format. This houses the best quality for BluRay movie rips. HD Audio and Video all in one format.
3GP: Google's own special format of MP4
ASF: Advanced Streaming Format, no longer widely used or seen as there's new compressions that house better quality in a smaller size.
WMV: Windows Media Video, just another video format mainly used by Microsoft products.
BIK: Bink Video is a highly compressed video format with no audio. The audio is usually streamed from a separate source on top.

AUDIO Formats
WMA: Windows Media Audio, an audio format mainly used with Microsoft products. Has recently started dying out.
MP3: Highly compressed audio file mainly used with portable media players and smart phones. Originally an Apple based format for iPods.
AAC: Early version of MP3 and M4A, not as much compression, larger file size.
FLAC: Free Lossless Audio Codec, uncompressed no lost audio quality, same quality as the studio recording.
MIDI: Musical Instrument Digital Interface, not widely used anymore. Used in old school gaming and applications as there weren't audio cards able to handle more than basic audio beeps and sounds.

IMAGE Formats
jpg/jpeg: Joint Photographic Expert Group, these do not allow transparency. Always go PNG with transparency.
gif: Graphics Interchange format, this allows for baisc animation on a web page. Kind of like short videos that are only up to 10 seconds long.
PNG: Portable Network Graphic, primarily used due to it not having much in the way of Compression, so images are obscured after saving. Allows transparency, widely used in web design.
BMP: Bitmap Image, old school image format primarily used in old school gaming and graphics.
DDS: DirectDraw Service, widely used with OpenGL and DirectX in graphics processing in new games as they support Bitmapping and light shading all in one single image. Also supports 3D objects

Region Specific Acronyms
NTSC: National Television System Commitee. Mainly used in the USA, NTSC runs on 525 lines/frame and it's vertical frequency is 60Hz. NTSC's framerate is 29,97 frames/sec.
PAL: 625 lines/frame, but the framerate is slightly lower, being 25 frames/sec. Mostly found in Europe and Asia/Japan.
DRM: Digital Rights Management, basically a special protection software to fight piracy on movies and music. No longer widely used as it's easy to beat.

iOS Specific Files (iPhone/iPad/iPod devices)
pList: player List file, houses XML (see basic extensions) like code specific to iOS/Mac OS to read from to get info about an application on the device. Need specific pList editor programs to modify.
app: Application, much like a exe on a Windows computer, .app is the default extension of a folder on iOS that houses an actual app and files (like plist files) for the device to run. tools like iFunBox can browse through these.
No Extension: This would be a binary file you'd find in the .app folder. This is kind of like the exe of a Windows PC

Android Specific Files
db: Database file that houses information for different applications and files.
sh: a script file more widely used in Linux (android is based on linux), to execute basic code (like batch files on windows).
apk: fancy jar file for android, installer file for apps

Lithtech Jupiter File Formats
Lithtech Jupiter is Game System that came out in 1999 with the release of the game TRON 2.0, No One Lives Forever 2 and Contract Jack (few years later). These are the file formats for this engine.
REZ: Special Resource folders that house all the elements of the game you're working with (normally). You can trick the games into thinking your using REZ files by simply naming a folder something like "Game.rez"
PRF: The default save file for the engine. Do not modify this file. These are the default settings.
LTA: Lithtech Editable 3d models. Use tools such as ModelEdit (characters, weapons, other models) or Dedit (Mainly for Maps) to modify these files.
LTC: A compressed LTA file.
LTB: Lithtech 3D Compressed models. Using Model Edit, Model Packer, World Packer or Dedit to compile and get these files. The only way to modify these files is to use a hex editor or LTB2LTA.
RS LTB: RenderStyle LTB's are slightly different. These old the lighting elements for the game engine. These files can only be modified by a Hex Editor. You can not decompile these files back to LTA or LTC like you can a Model LTB.
DAT: These would be compressed World LTA/LTC files created by Dedit or World Packer. These files are not heavily modifiable unless you're an advanced user with a hex editor.
DTX: These are special image formats for the graphics of everything in the game. the engine can be modified to use PNG files, but it's not recommended.
FXD: ClientFX Files house the animated Effects you'll see in the game. Things like explosions, bullet holes on walls, blood spatter, etc. are all created from here.
LTO: A simple extension rename of a special DLL file. Mainly used to identify the Object.LTO file which holds links to all the objects and files in the game as well as server information.
DEP: This file simply links to the games install directory for all the files using Dedit.