bbaerst hi,
very briefly, photo-etched sets are thin metal pieces, all flat, that come on sprues just like the plastic which makes our kits. the difference is that they can achieve incredibly small and detailed parts using this method of manufacture (exactly how they do it, god knows!). the problem is that as it is cut/pressed metal, all the pieces are to all intents and purposes, "one dimensional", and require lots of fiddly folding and bending to make something like a machine gun (common in armour PE sets, less so in aircraft).
an example from eduard's site:
http://www.eduard.cz/./products/card.php?id_product=515&name=p-51&catalogue_nb=&type=1&pgroup=1&scale=&product_month=&product_year=&page_start=5
click on "instruction sheet and you'll see how the bits are meant to be used.
resin sets will look and feel like the plastic bits we are used to, but instead of injection molding, they are cast. because there is less automation here, the maker of the resin mold/cast can really go to town on the detail. the down side is that instead of a small neat attachment to their sprues, resin parts are usually attached to a resin casting block all along one side/edge of the item in question. as a result, it can involve lots of careful cutting and sanding just to "free" the part; a pain because resin is sometimes more brittle and less forgiving than regular plastic.
here's an example of some resin stuff by verlinden from the hannants' site:
http://www.hannants.co.uk/cgi-bin/search.pl?Mode=view&Database=cat&R=VL1485
hmmm...that wasn't exactly brief was it?[:0]
![Tongue [:P]](/FSM/CS/emoticons/icon_smile_tongue.gif)
hope it helped though.
regards,
nick