I want to learn more about contents menus like the one on the right of the apple developer guidance that moves as you scroll down, but I can't find the right terms to search for: https://developer.apple.com/design/human-interface-guidelines/foundations/accessibility
1 Answer
Sidebar TOC
All the elements placed in a box on one side of the screen are called sidebars, among which are the sidebar social links, sidebar menu, sidebar navigation and the sidebar TOC which is a navigable table of contents within each page.
You will find a better example on this page with dot navigation plus an expanding index menu.