.APP File extension

An app file is an application bundle that runs under Mac OS X. APP files are executable files similar to .EXE files in Windows and run when double-clicked.

Because APP files are Mac OS packages, you can right-click (or control-click) an application and select "Show Package Contents" to view the files contained in the package. These include Resources used by the application, executables, property list (.PLIST) files, frameworks, plugins, icons, and other files. In Windows and Linux systems, it may be possible to view the contents of a Mac OS X application as if it were a folder. A decompression program like WinRAR may also be able to extract files from a Mac OS X application on other operating systems. NOTE: Files within an application package should not be edited or moved, since changes may prevent the program from running correctly.