Deluxe Hot Toys figure.
Usually means you get two headsculpts and two outfits with the figure, and it has moveable eyes.
However if they released Darth Vader as a DX, all it would mean is that they would charge you $50 more for a regular figure in a nicer box.
Why regular ? If it was a DX it would mean PERS which would mean a swappable portrait with a Shaw head