There's also a large number of diagrams in the Appendix section of the "Hitch Hiker's Guide to the Empire", one of which covers the refused flank.
To me, the difference between a "refused flank" and a "weighted flank" approach to battle lies in the primarily defensive nature of the first, and offensive nature of the second. Allow me to elaborate:
In a refused flank, you are trying to counter some enemy advantage, whether this be overwhelming numbers, or, as Tsetsen correctly pointed out, superior manoeuverability. The aim of the refused flank is to focus your troops in a close formation, protected on two sides by the table edges (flank and rear), and projecting their combat power out towards the other two (front and other flank). The force is thus deployed for each unit to cover the other's flank, and all units collectively covering each others' rears. You are trying to keep the enemy away from your flanks/rears and force them to fight on a very narrow front. This implies a defensive stance - as soon as you start to move more than a few inches, your units abandon the safety of at least one of the table edges, and may have to break formation, neither of which is a good idea against an enemy with superior numbers and/or manoeuverability. Atchman is quite correct in asserting that a small holding force on the "refused" flank can be highly useful to discourage enemy attempts to turn and encricle the defended flank.
In a weighted flank, however, the aim of the army is to hold the line as per regular, but to reinforce one flank so strongly that it should except to crush the enemy's forces there, thus turning the enemy flank, allowing the flank force to thunder down the enetire enemy battle line. Normally, the heavy hitters in the weighted flank will be offensive units - heavy cavalry, for instance, and/or a steam tank - with the intention of bashing the enemy up good before he has a chance to punch through the other, lighter flank of your army. A weighted flank can therefore also be described as a (left- or right-) "Hook" or simply as a "Flank Attack".
Of course there is a lot of grey area and overlap between the two, depending on the degree of defensive/offensive-mindedness of the general commanding, the exact composition of the armies in question, etc. etc., but these, I believe, are the main differences.
And no, I'm not much of a Buffy fan I'm afriad
Cheers!
--GH