wesnoth/images/dialogs

This directory contains the images used to assemble dialogues.  Each group of
images is named by the part before the first dash, which is a style
referenced by name in the Wesnoth UI code.

The 'transparent' images have some alpha transparency; they look like
smoked-glass overlays on the terrain or whatever else is underneath them.
The 'opaque' images are geometrically the same, but opaque.