"Content Type" is a Drupal term, which is fairly self explanatory. If you want to geek out, think of them as an object of a particular set of content, where individual pages (or nodes in Drupal parlance) are instances of that object.

This is also a good example of a "parent" page with "child" pages listed. In order to manage the images and text that display below, you must edit the thumbnail and summary fields on the "child" pages such as on the Entity Index Page itself.