Pages on the web are files interconnected by links. The pages are stored in a hierarchical structures of folders or directories. This page is in a folder called 'devices' which contains an index file and several folders, each of which contains examples of devices such as a central heating controller, a telephone, and so on.
Each example of a device consists of a main file and perhaps some associated image files.
The index file contains links which point to the main file for each example. That main file, in turn, may contain links which point to the image file(s).
In the HTML code, the links are represented as some magic syntax plus the address of the target. So, the index file will list the addresses of all the main files for the examples. There is no automatic back-pointer.