This image clearly shows the difference between the translucent and opaque alignments you can have your Vision window blind set to.

When the opaque parts of the fabric are aligned, as they are on the left hand blind, you get a blackout effect that dramatically reduces the amount of light coming through the blind. The translucent arrangement, as seen on the left hand blind, still lets a lot of light through but at the same time reduces heat and glare, letting you enjoy a light and airy room in comfort.

The ability to move from a blind that keeps the light atmosphere of a room, to a total blackout effect is what makes Vision blinds so popular as window blinds in conservatories, allowing you to control the light and privacy in the room.