My understanding of Damascus steel is the way in which it is made. When polished, it has a very distinctive pattern of light and dark areas on the surface of the steel. If my recollection serves, this indicates a non-homogeneous mixture of higher and lower carbon steels (banding) in the matrix. I believe 'twist' refers to the forge welding of the steel around a rod of the correct diameter. If either the Damascus or the forge weld is not done well the barrel will not be a 'good' barrel.