A "broodmare" is a female horse that's been bred. A "proven broodmare"
is one that's carried a foal to term.  A "maiden mare" is a female horse,
four or older, that hasn't been bred. "A broodmare prospect" is an unbred
female horse that the seller wants the buyer to think might be able to
produce something worthwhile, although most often the mare's
performance, if any, did not enhance her potential value in the stud (see also,
Somethingroyal).  A "[insert acronym here] producer" is a broodmare that
has produced a foal that has done something worthwhile; i.e., "ROM producer",
"AQHA Champion producer", "stakes producer", "G-1 stakes producer", etc.
(From former to latter, the price of poker goes up considerably.)