The Free On-line Dictionary of Computing (30 December 2018):

BibTeX
bib

    A Tex extension package for bibliographic
   citations, distributed with LaTeX.  BibTeX uses a
   style-independent bibliography database (.bib file) to produce
   a list of sources, in a customisable style, from citations in
   a Latex document.  It also supports some other formats.

   BibTeX is a separate program from LaTeX.  LaTeX writes
   information about citations and which .bib files to use in a
   ".aux" file.  BibTeX reads this file and outputs a ".bbl" file
   containing LaTeX commands to produce the source list.  You
   must then run LaTeX again to incorporate the source list in
   your document.  In typeset documents, "BibTeX" is written in
   upper case, with the "IB" slightly smaller and with the "E" as
   a subscript.  BibTeX is described in the LaTeX book by
   Lamport.