Dynamic tiles

Are dynamic app tiles desktop or web/mobile; or both?
They are not dynamic apps they are apps with dynamic tiles in the app center.
Desktop and Web. mobile has no app center. You build individual discrete mobile apps.

Dynamic tile

businessoverviewweek is a slightly unusual App as it designed as a Dynamic Tile to display dynamic data in the Lianja App Center, rather than an App to load and run.
For any App, switching to the Apps Workspace lists all the scripts in the Files explorer in the Sidebar.
To specifically see the code for a Dynamic Tile, you can open the Settings for the App from the ModeBar and look under App Center Tile.