Publisher
The organisation that issued a book or report, named in the reference so the reader can identify the exact printing.
Books need a publisher; journal articles generally do not, because the journal name already identifies the source. APA 7 simplified the field considerably: no place of publication, and no “Inc.” or “Ltd.” — just the name.
Chicago still wants the publisher (the 18th edition stopped requiring the place of publication), and imprints matter there: a book from an imprint is cited under the imprint, not the parent conglomerate. Where the author and publisher are the same organisation, most styles name it once.
See also
Place of publicationThe city where a book was published — once standard everywhere, now dropped by APA 7 and, for modern books, by MLA 9 and Chicago's 18th edition.Reference entryOne complete record in a reference list, containing everything a reader needs to find the source themselves.Corporate authorAn organisation credited as the author of a work, used when no individual is named.