The thumbnail layout allows users to explore their content using a gallery type display. Each piece of content will display a thumbnail, either generated from its display (in the case of reports and dashboard tabs), from its assigned thumbnail image (in the case of storyboards and discussion streams), or a generic thumbnail icon (in the case of content that hasn't been run yet, or been assigned an image).
This list layout allows users to explore their content using a text based display. Each piece of content still has a thumbnail associated with it, but in order to view it the user will have to view content information through the activity stream panel. The list view generally allows users to view more pieces of content on the screen at any one time, making bulk actions easier to perform.
The list view allows each user to select what information they want to have displayed on the page through the columns menu. As each user interacts and acts on content differently, unique groupings of columns allow them to make the most of this page.