What do I call them?
LibGuides or Guides or Web Pages?
"LibGuides" refers only to the web-based software package by SpringShare. The consensus from the Website Development Committee is that the general term "guides" is a category that refers to librarian-created web pages that are aids for subject- or course-based research; in this category there are "subject guides,", "course guides," "subject gateway pages," "topic guides," and currently, "general purpose guides." The rest of the site comprises web pages on the Drupal platform.
It is important internally that we don't confuse LibGuides (the package) with the pages created with that package. (Think of "LibGuides" as being akin to "Microsoft Word." You would never refer to a document created in MS Word this way: "Just read that MS Word I sent you.")
Are they called Tabs or Pages?
For consistency's sake, call them pages. SpringShare calls them pages, and so do users.