Three things that headings do…
This isn’t a link to an article elsewhere… I just thought I’d post this thought, which won’t be news to many people here, but I’ve found it useful when discussing principles of design and effective communication to be explicit about these points.
1) A heading communicates the start of a new section. This assumes the heading is reasonably well designed. It means that a reader can scan a page and pick out the sections.
2) A heading communicates hierarchy. Sub-headings will typically be in a small font size, or not bold etc. Again, it needs to be easy to pick out when scanning.
3) A heading communicates semantic information about the content. This assumes that someone gives some thought to the wording of the heading, and succinctly describes what the content actually is about, rather than just using the heading to fulfil the first two functions.