The comb on the stock is the portion of the stock you rest your cheek on.
Yes, Zippy and I are talking about the same thing - I was just trying to describe it to you ( maybe in a clumsy way ..).
If you look at the specs on a shotgun in a catalog it will tell you how much drop there is at the comb and at the heel (the recoil pad).
Yes, casual Trap shooters shoot Trap will all kinds of "field" guns - meaning a gun with an angled stock. Most serious Trap shooters go to a "monte carlo" stock that is parallel to the rib - for lots of reasons ( adjustability, consistent sight picture whether you're shooting in a winter coat or a T-shirt.
A "field" gun is just a term applied to a stock that is angled from front to back - and it can be in a pump, semi-auto, SXS or Over Under - and at virtually any price level.