Appimage

AppImage is a monolithic packaging format for linux applications. It contains all dependencies in one file that is composed of an executable with a tacked on filesystem.

On most distros, all one has to do is download the .AppImage file, make it executable chmod +x $AppImage, and execute it. This doesn't work in nixOS out of the box though (can someone explain why?)

Running an AppImage file on NixOS

$ nix-shell -p appimage-run
$ appimage-run $AppImageFile

How AppImage files are packaged by NixOS

See the nixpkgs manual on wrapping AppImage. Basically what is done is the AppImage is extracted and the dependencies are added as nix build dependencies.