What is "Cross-referenced"?
Cross-referenced is library lingo. Are you surprised? What it really means is that a term, thing, person, etc. notated in a particular article will show up in another article as important. While you may be searching for the biographical article on Gustav Mahler, others with pertinent information about him will also appear on the screen. Very slick.
What is a "See" or "See also" term mean?
You'll see this used in a number of print sources (if they're any good!). "See" tells you that although the term you used is valid, they have placed the information you want under another term (Ex. Conductus Motet SEE under Motet A II) "See also" means the same thing as cross reference. It reminds you of Netflix. Like this movie? SEE these suggestions ALSO.