The application display template (ADT) framework allows portal administrators to override the default display templates, removing limitations to the way your site’s content is displayed. With ADTs, you can define custom display templates used to render asset-centric applications.
Usually, when you need to modify the UI of a Liferay portlet, you can do so using a hook (e.g., HTML-related change) or a theme (e.g., CSS-related change). It’d be nice, however, if you could apply particular display changes to specific portlet instances without having to redeploy any plugins. Ideally, you should be able to provide authorized portal users the ability to apply custom display interfaces to portlets.
Be of good cheer! That’s precisely what Application Display Templates (ADTs) provide–the ability to add custom display templates to your portlets from the portal. This isn’t actually a new concept in Liferay; some applications already had templating capabilities (e.g., Web Content and Dynamic Data Lists), in which you can already add as many display options (or templates) as you want. Now you can add them to your custom portlets, too.
Some portlets that already support Application Display Templates in 7.0 are Asset Catgories Navigation, Asset Publisher, Asset Tags Navigation, Blogs, Media Gallery, RSS, Breadcrumb, Language, Navigation Menu, SiteMap, and Wiki.