AppDir

The AppDir format for application directories was first introduced by ROX Filer. http://rox.sourceforge.net/desktop/AppDirs.html

The AppRun file is the main entry point and is what is executed when the AppDir (or the AppImage containing it) is launched. The AppImageKit project provides an AppRun.c implementation, but you are not bound to use that one - you could also write your own implementation in C, sh, or just use a symlink to the main executable - the only requirement is that AppRun will successfully launch the main payload application.

The basic structure of an AppDir which can look something like this:

AppDir
└── AppRun
└── your_app.desktop
└── your_app.png
└── usr
    ├── bin
    │   └── your_app
    ├── lib
    └── share
        ├── applications
        │   └── your_app.desktop
        └── icons
            └── <theme>
                └── <resolution> 
                    └── your_app.png

Replace <theme> and <resolution> with (for example) hicolor and 256x256 respectively; see icon theme spec for more details.