I'm not quite sure what was meant before with "footer" file. Renamed it to "head tag"
What does "header file" mean?
it refers to most CMS / websites implementing the practise of having a header file and a footer file for easy modification across sites. I think the "footer file" is more famous/well-known but most people would understand header file as well, right?
I don't think most people would understand what is meant by it. Maybe something would be better like "added to the &lgt;head>" tag which is often defined in a "header.php", "header.tpl" or "header.twig" template file.