There are the 3 basic stack positions for vertical blinds, draperies, and vertical honeycomb shades

vertical-blind-stacks
Stack positions are oriented looking at them from the inside, where the vertical blind is mounted. The Left stack position has the vane slats stacking on the left. They will draw to the right where the vanes can be tilted closed. The Split Stack position, sometimes referred to as center open, draws the vanes to the center. The Right Stack position has the vanes stacking on the right. They will draw to the where the vanes can be tilted and closed. Stack position is an option when ordering a Vertical Blind Headrail.
Control Side refers to the side the controls are on when facing the blind from the inside. This option refers only to Cord & Chain and can either be on the side where the vanes stack, or on the opposite side. Wand Control will always be on the same side of the vane stack.