kerning is the spacing between letters in a horizontal line of type. You think you never notice that, but you do. When the kerning is too tight (not enough white between characters), it's crowded and hard to read and you start hating the book for no content-related reason; ditto when it's too loose. A good typesetter sets the overall kerning given the font and page specifications, but then checks and adjusts it pages where there's an illustration, a weird giant word, or something else throwing off the normal line. Readers pay attention to kerning when typesetters don't--in newspapers, where you'll often see a really long word (often an email address or URL) bumped down to the next line, leaving half a line blank above...or a single word stretched out to fill the fully justified space...l i k e t h i s.
leading is like kerning but on the vertical; it is the space between lines. 0% ledding is the least you can do without the bottom of a p touching the top of an l. That's ghastly to read, though, as you might imagine; it's the sort of Gideon's Bible all-black page that makes you close the book. Most typesetters don't adjust leading page to page--a reader's eye will notice that, but leading can sometimes be tweaked very slightly to prevent widows and orphans.
widows and orphans are lonely words or partial lines. A widow is the last line of a paragraph that lands on the top of a page separated from the rest of its paragraph. An orphan is the first line of a paragraph that falls at the very bottom of a page, again separated from its brethren. The way to remember which is which is the decidedly unsexy line, "a widow has no future, but an orphan has no past." Sad and spooky, no?
laid paper has a far higher sexiness quotient. It is an old-fashioned way of making paper that involves setting it in a ribbed mold of crosshatching chains. When you take the paper out, the grooves of the chains remain. Some paper companies but there logo into the mold, also. This is rare now, but you do see it occasionally--especially in limited edition books meant to be enjoyed as objects as well as stories. In researching this article, I found out that laid paper is even rarer than I thought, because some that appears to be so is actually some other kind of paper with a laid-ish stamp pressed overtop. It's like those restaurants that paint the grill marks on the burgers--shocking!
perfect binding is when the book-block (all the pages in the book, folded together in signatures) has glue basted on the spine and then the cover pressed overtop. This is how your paperback book was made unless it is very fancy-schmancy indeed. This is a less expensive way of binding than case binding, but unless you are planning on throwing your book at someone, it makes little difference to the average reader (I believe it is a problem for book collectors to have glue in a book, but I don't know the details of that).
case binding is the fancier way, and what you generally get with hardcovers. Signatures of pages are stitched together and then stitched into the spine of the cover. Meh. (Note: I have a giant chip on my shoulder about hardcovers and can't be trusted to offer fair and balanced reporting on this subject).
signatures are sets of pages made by folding a single sheet of paper. For instance, if you were to print on both sides of an 8.5x11 inch sheet, you'd have to print pages 1 and 4 on the page, and 2 and 3 on the front, then fold to create a four-page signature of 8.5x5 pages. But 4-page signatures are rare; usually they are 16 pages, involving horizontal and vertical folds, and are very confusing. Some of my most humiliating arithmetical debacles involve signatures. Also, this was the only definition I couldn't find an online source to double-check myself, so let me know if I've erred (actually, on the others too; the Internet is rumoured not to be infallible, though I doubt this myself).
There--doesn't that make you want to embrace real books, or at least feel one up?