Parts of a Book
This post is for people who aren’t sure how to describe their book to us and just need to know a little bit about book lingo so we’ll both be on the same page.
When you’re describing the cover of the book:
Cover. This is the part you see when the book is closed, whatever it’s made of. There’s the front cover, the back cover, and the spine cover. It should all be connected.
Spine: The “backbone” of the book; the part of the book that you see when you shelve it, the part you hold when you’re balancing the book on one hand while you read it. A spine can be very plain or embellished.
Raised ribs or bands: The horizontal lines on the spine, giving a 3-D effect because there’s something under the leather. These used to have a function, but that was a few hundred years ago. Now they are ornamental. Height and placement can vary.
Since these are ornamental, raised ribs do not have to be there, or other, more artistic arrangements of the materials under the leather can be made. Some rebinders add crosses, fish, or other decorative touches.
Boards. These are the front and back parts of a hardcover book, like a leather hardcover Bible. A board is made of thick, hopefully non-acidic, cardboard on the inside, but some older books have very acidic boards. It can be covered with paper, cloth, leather, or some other kind of material. On an antique family Bible, a thicker cover is made of several boards on top of each other, carved out in the middle, and then it’s covered with leather.
When you’re describing the insides of the book:
Text block (or book block): The pages; the “guts” of the book. In a Bible, this includes the Bible text plus any addenda like concordances and dictionaries, as well as the title page, family pages, and any personal note pages.
Sewn binding. This means the book is comprised of groups of pages that are folded together, and they’re all sewn together at the spine edge. If you look down on the top of the book, you should see something that looks like little booklets side by side. They are called “signatures.”
You will hear terminology such as “Smyth-sewn” or “lay-flat” to also describe this.
You should be able to get to the middle of one of these signatures and see sewing running up and down the middle of it. 
Glued binding. This means the book has pages all cut to the same size and stuck up against a glue strip under the spine. It means trouble when the glue strip pulls away or shrinks. Heat will cause that. This is also ironically called “perfect binding.” It will generally mean that the binding will need to be reinforced during the process of getting a new cover. You should know that it is not possible to take a glued text block and make it smyth-sewn, since there are no folded edges. There are other ways to make this kind of book functional, so don’t lose heart, but they involve losing some of the inner margin space.
Hinge Cloth, or Mull: This is the mesh stuff over the binding. You’re not actually seeing sewing, but the reinforcement material. Actually, you’re not supposed to be able to see it, but if your Bible is broken along the hinge, you can see things you’re not supposed to see.
Hinge cloth is what actually attaches the cover to the book, under the end page. Many modern books use what is called “super.” They fall apart because it is not at all “super.”
When you’re describing other things you can see:
End pages: These are generally the long pages that are glued down to the inside of the cover and form the first page of the book (often colored, and in a Bible especially, made of leatherette, which is that standard coated paper).
Lining: In an edge-lined Bible, the lining is a material adhered to the insides of the cover, usually tucked under the folded edge of the outside leather all around. All edge-lined Bibles on the market today are not lined with leather, however. It may be leather, but it could be a bonded leather or a synthetic material, or it could even be cloth or paper. In a few cases, the lining material may only be a thin latex sprayed over stretchy fabric to look like leather. (That is deceptive.)
In the case of a leather-lined or edge-lined Bible, the end page is only a half end page — just the free portion.
Headbands and Tailbands: These are little strips of cloth, often striped, attached to the spine edges of the pages at the top and bottom of the text block. These, like the raised ribs, used to have a real function, but today, they make the book look nice and cover up raw edges. They are merely decorative and are not the binding. The ribbons are tucked under the headbands.
Page edges: Generally, most Bibles on the new market will have gold or silver page edges, and that matches the imprinting. It is usually not high quality and it will wear off quickly, especially if exposed to water. Some rebinders offer art gilding services, which involves adding a color, such as red, under the gold or silver on the page edges.