Its an instrument that uses one or more mirrors to reflect sunlight with a mechanism to track the sun and move the mirrors allowing for continual reflection across the daylight skies.
These instruments are most often used for solar power arrays to concentrate sunlight or heat to generate power. But now you can have a mini version for your home garden.
Wikoda has come up with a mini heliostat for the home user. Its called the Sunlight and at 30′ can reflect sun as high a 42′ above the horizon line or 13′ below the horizon line. The website speaks mostly about adding natural light to rooms with east or west facing windows, but not much yet about the benefits in the garden. I am waiting for correspondence from the company to learn more.