The “Convert” button appears on both theme and component pages. It will allow you to convert a theme to a component or vice versa through the admin interface. Most Discourse admins will never need to use it. Themes and components found at theme already include the correct designation.
This should be covered in our Beginner's guide to using Discourse Themes, but the basic idea is:
- Themes are considered to be the baseline of your Discourse site’s styling. Often sites offer multiple, user-selectable themes.
- Components are meant to be added to themes to extend style and/or functionality beyond your basic theme(s).