Where things sit on a page, the space around them, and the edges a printer cuts.
Also: double-page spread, DPS
The two pages that face each other when a book lies open. The spread, not the single page, is what a reader sees and what a designer lays out.
Readers never see one page alone, so designers lay out both at once: a picture can cross the fold, and the two pages balance.
The recto is the right-hand page and carries odd numbers; the verso is the left-hand page and carries even ones. A verso is always the back of the recto before it.
The right-hand page, always odd-numbered. New chapters usually open here.
The inside margins where two pages meet at the spine. The thicker the book and the tighter its binding, the more of the gutter disappears into the fold.
A thick book doesn't open flat: text set too close to the spine curves away into the fold. Widen the inside margins to bring it back.
Also: head, foot, inside and outside margins
The four empty bands around the text: the head at the top, the foot at the bottom, the inside by the spine and the outside at the edge (the fore-edge). Their proportions set the feel of the whole book.
Narrow inside, wider outside, widest at the foot: across a spread the two text blocks sit together and the page doesn’t feel like it is sliding down.
Also: type area, type page
The rectangle inside the margins where the text is set. Its width, height and number of columns are the skeleton of the page.
Everything but the running heads, folios and bleeding pictures stays inside this area. Its shape is the first decision in a page design.
Also: running header, running title
A line repeated at the top of each page, outside the text block, saying where the reader is: the book, the chapter, the section. At the foot of the page it is a running foot.
Here the verso names the guide and the recto the walk, so a reader flicking through always knows where they are.
Also: page number
The printed page number. Pages count from the first leaf, but not every page shows its folio: blank pages and openers often leave it out.
At the outside edge it can be found with a thumb while flicking; a contents page or an index sends readers to it.
Artwork extended beyond the edge of the page, usually 3 mm, so that it still reaches the edge after the printed sheet is cut. The edge it is cut to is the trim.
Guillotines drift by a millimetre or two. Artwork that runs 3 mm past the trim means a slightly off cut still leaves colour at the edge, not a white sliver.
A picture or colour that runs right off one or more edges of the page, with no margin around it. Bleeding one edge is a bleed off that side; all four is full-bleed.
Run off every edge, a photograph stops being an illustration and becomes the place the reader is standing in. Magazine feature openers often do this.
Also: live area, safe zone
The area inside the trim where anything important must stay: words, page numbers, faces. Outside it, the cut might take it off.
The trim can wander inward too. Keep words and faces at least 5 mm inside the trim, even on a picture that bleeds.