Layout for printing (on paper, for those who still do that) I presume.

beej71 · 2025-02-05T16:32:09 1738773129

Exactly this. There are three main differences:

1. The margins are offset in two-sided, alternating pages. 2. The page numbers are justified alternately left and right in two-sided, and the page header differs left and right. 3. Sometimes a blank page is injected with two-sided to make a chapter start on the correct side of the book.