I have a bibliographical reference:
[Author] [book name]-5th ed.,pp.3-6,ch.3.
What does the "pp" stand for? I don't recognize this abbreviation.
The "pp" refers to a page range, e.g. "pp. 3-6" means page three through page six.
I'm not entirely sure what citation style you're using, but this convention is used in the MLA citation style, as well as some other citation styles that I can't remember off the top of my head.
LiteratureSE user Aethelbald has suggested that:
pp stands for the Latin pari passu meaning side-by-side or at-the-same-rate or on-an-equal-footing... here it means equally and throughout pages 3 thru 6.
Other contributors, however, disagree. Kevin notes that:
Wiktionary also lists "p." as meaning "page," singular, and specifically describes "pp." as the plural of "p." This is obviously not a productive pluralization method
and hobbs adds that:
there are a few cases, in Latin-derived abbreviations, where a plural is made by doubling the last letter. "MS." => "MSS." (manuscript/s), "op." => "opp." (opus/opera). This is one of those, since "page" has its origin in "pagina".