The best way to describe a bevel is when it seems that the frames/outlines etc of the combine are coming out of the page, slightly. When it's on, it is beveled and there for things look more 3d, and techy, if you will.
It's hard to tell what it does if you are not looking for it, so I don't blame him at all for posting here. To someone not completely literate insofar as design is concerned, for all they know, bevel could be some weird way of re-directing Darkness Messages, or displaying their data to them. This would be un-desirable and thus he asked prior to turning it on.