This command brings up the Passages dialog, where you can browse through all the passages that come with your installed database modules, as well as any custom passages you've written yourself and placed in the User-created content folder (to find out, or set, the location of your User-created content folder, look at the Paths tab of the Preferences dialog).
By selecting from the Show lists, you can direct Acces to display Title or Filename and Length or Flesch-Kincaid Reading Level for each passage.