Section is similar to a div but used to group related content. You will notice that the section in your quoted text has no classes but does include identifiers, roles, epub-type, etc.
The ID is likely used in the ToC instead of pointing to the chapter file, you would get href="part0007.html#hd-chapter001". Add further ids for subchapter entries.
The href to the ToC allows you to go back to the ToC by tapping on that entry. A vestige of old practices. Remember when you would see Last:Next:ToC at the top and bottom of chapters?
An epub-type is part of ePub3 attributes allowing improved semantics. Originally, it was hoped/hyped that epub-type would improve accessibility but other than some limited success with footnotes, this did not happen.
OTOH, a role is an ARIA attribute used to expose information to assistive technology. There is a lot of overlap which is why it was originally hoped to use epub-type but support never materialized.
See the
EPUB Type to ARIA Role Authoring Guide for more information.