<name>.desktop - for programs this file is optional, if included it will be added to /usr/share/applications to appear in the application launcher (which isn't relevant for all programs, like run). For panel plugins this is required and will be deployed to /usr/share/xfce4/panel/plugins so that the plugin is available to use.

Developing Shell Components

If you're planning to contribute by developing a program or plugin, then you should consider the following:

If you plan on writing a program, check that it is a shell component - things considered shell components are those that are typically part of explorer (including explorer itself) that are not really a program in their own right
- This may sound vague, examples of this is: the run dialog, the autorun dialog, winver, explorer file browser, control panel (as part of explorer), etc.
- If unsure, check the issues page for additional-programs tag to see if what you want to work on is there, if not, open a new issue and it can be discussed where it belongs
If you plan on writing a panel plugin, it is always considered a shell component, as the panel is part of the shell
If the program is not a shell component, it belongs under /windows rather than /shell