Once you have written a document with labels, references and citations,
it can be nice to read it like a hypertext document. RefTeX has
support for that: reftex-view-crossref (bound to C-c
&), reftex-mouse-view-crossref (bound to S-mouse-2), and
reftex-search-document. A somewhat fancier interface with mouse
highlighting is provided (among other things) by Peter S. Galbraith’s
bib-cite.el. There is some overlap in the functionalities of
Bib-cite and RefTeX. Bib-cite.el comes bundled with
AUCTeX.
Bib-cite version 3.06 and later can be configured so that bib-cite’s
mouse functions use RefTeX for displaying references and citations.
This can be useful in particular when working with the LaTeX xr
package or with an explicit thebibliography environment (rather
than BibTeX). Bib-cite cannot handle those, but RefTeX does. To
make use of this feature, try
(setq bib-cite-use-reftex-view-crossref t)