CDX is a type of plywood.
Basically, plywoods are thin veneer sheets that are glued and held together with linking plies. ... If so, it therefore, means CDX has the most number of knots and defects, making it a lower grade plywood. C in CDX means one side of the plywood is of grade C, and the other is of grade D.
CDX plywood most popluar is use pine veneer.