A separate programme:

• generates a list of references
• from citations referencing a bibliographic database.

Documentation:

• Section 4.3 of LaTeX: A Document Preparation System, 1986 (and Appendix B).
• Using BibTeX: PDF (Postscript, .tex, .bib, .dvi)
• Hacking BibTeX: PDF (Postscript, .tex, .dvi)