Featured images (also sometimes called Post Thumbnails) are images that represent an individual Post, Page, or Custom Post Type. When you create your Theme, you can output the featured image in a number of different ways, on your archive page, in your header, or above a post, for example.

Themes must declare support for the Featured Image function before the Featured Image interface will appear on the Edit screen. Support is declared by putting the following in your theme’s functions.php file: