An application template is basically an application minus some information. For example, there is no GUID attached to it, so you can import a template multiple times. Typically, a template allows you to download an application of your choice from a website which offers a plethora of downloads.
If you want to share application templates, you can export an existing application as template by choosing “Application Template” as output file type for File –> Export. After that, you can add placeholders manually to the exported XML. When a user imports an application template with placeholders, he will be asked to insert values for them.
To add a placeholder, just add:
<placeholder name="This will be shown to the user" />
...to the exported XML. You can add as many as you like. The user will only be prompted once for multiple placeholders with the same name.