AC.MSK.SU contains a searchable database of thousands of file extensions with detailed information about the associated file types. Each entry contains information about the file format, a description of the file, and the program or programs that can open the file. Programs for opening the files are listed for Macintosh, Windows, and Linux platforms
What is a File Extension?: File extension is the suffix at the end of a filename indicating what type of file it is.
If you come across a file or e-mail attachment with an unknown file extension, you can look up the file association using ac.msk.su.
For an overview of common file types, see list presented below, which includes a list of important file formats you should know.