House Rules are the lists of instructions issued by publishers to authors, printers and editors, etc, to provide consistency in the presentation of texts. These cover such matters as whether to use single (') or double (") inverted commas, when to use upper case letters at the starts of words, and which spellings are used for words where English has no final policy. Each publishing company (traditionally known as 'a house') has its own list. They often disagree on small details. Some have been published, e.g. the OUP's Hart's Rules. Newspapers sometimes call them Stylebooks;. or Style Guides, e.g. The Guardian Stylebook.
Similarly, academic departments provide guidance to students on such matters as layout, sexist language, and referencing formats. Of their nature, these are much less detailed than publisher's House Rules or newspaper Stylebooks. But good students take note of what guidance they are given, and only depart from it when they have good, conscious grounds for disagreeing with their teachers.