Every once in a while, you get a file from a client or vendor and have no idea what app it was created in. It doesn’t open in Photoshop, Graphic Converter, Quark or InDesign, so what could it be? 
Well, you can always check over at FileInfo.net. FileInfo.net contains a searchable database of file extensions with detailed explanations of each file type. Every file extension entry contains information about the file format, a description of the file, and how to open the file. Programs for opening the files are listed for both the Macintosh and Windows platforms. The information can be browsed by file type:
- Text
- Data
- Image
- Audio
- Video
- Web
- Fonts
- Plugin
- System
- Executable
- Compressed
- Developer
- Backup
- Disk
- Game
- Misc.