Panels slide out from the right and are the main content areas of pages. On simple Pages, Panels are made up of a single WYSIWYG editor, while on list tools like News or Calendar, the Panel contains a list of items like articles or events.
Panels are available to manage content at every level of the site. At the top level, the Panel lists all pages in the site. At the page level, Panels manage page content and items. At the item level, Panels display the various content associated with the item, and so on.
Tabs are any supporting content for the current Panel. Tabs are always located on the right side of the content Panel. For example, in a blog article, Tabs contain the primary content in the first Tab, and additional supporting content like publication Details, Picture, Location, etc. on the right of the Panel.