This page allows you to define Concrete CMS's thumbnail generation behavior; that is, how and what types of thumbnails are generated when you upload an image to the file manager. It also allows you to create new types of thumbnails should you require them. To edit a thumbnail type, just click the name and you'll be sent to the thumbnail detail interface: 



You can also click the "Add Type" button in the upper right of the listing page to add a new type of thumbnail into the mix if you like.