A link (or at least a page reference), from the bibliography to the citing command, is often useful in large documents.
Citeref is the older, and seems to rely on rather simpler
(and therefore possibly more stable) code; it produces a list of page
references, only. It doesn’t interact well with other citation
packages (for example,
cite), which probably reflects its
antiquity (it’s derived from a LaTeX 2.09 package).
lists of pages (“5, 6, 7” comes out as such, rather than as
“5–7”), but neither package repeats the reference to a page that
holds multiple citations. (The failure to collapse lists is of course
forgiveable in the case of the
backref, since the concept of multiple hyperlinks from the
same anchor is less than appealing.)