When analyzing the yarn count, the ply and yarn size are import. This refers to the direction of the twisting. All yarns are twisted to keep the fibers together. A 2 ply has 2 ends twisted together. Yarns can have a high or a low twist.
High twists have more twists per inch than a low twist yarn.
A high twist yarn generally is smaller than a low twist yarn. Yarn is 1 color. A 2 ply yarn with each ply a different color. Each ply is dyed a color, then twisted to form a 2 ply yarn. The 2 colors from a distinguished pattern.