What is content pane and embed?
Many modules provide add-on functionality for Views. Chaos tools suite (ctools) provides the Content Pane display, which is a way to embed views in other areas of your site using advanced context passing. The views are not treated as pages and you can therefore embed them multiple times, just as you can with blocks, but with blocks your context handling is very limited.

For one good example of where and how to use it you may look at Panels module.

Some tutorial here:

Drupal Tutorial - Panels #6 : Related Content With Views Content Panes | WDTutorials.com